Lithium-containing transition metal composite oxide, positive electrode active material for lithium secondary battery, positive electrode for lithium secondary battery, lithium secondary battery, and method for manufacturing lithium-containing transition metal composite oxide

ABSTRACT

This lithium-containing transition metal composite oxide includes secondary particles that are aggregates of primary particles into or from which lithium ions are dopable or dedopable, and satisfies the following conditions:
         (1) the lithium-containing transition metal composite oxide is represented by Formula (I),       

       Li[Li x (Ni (1-y-z-w) Co y Mn z M w ) 1-x ]O 2   (I)
         (2) from X-ray photoelectron spectroscopy, a specific γ is calculated for each of the surface of the secondary particle and the inside of the secondary particle, and when the γ value of the surface of the secondary particle is referred to as γ1 and the γ value of the inside of the secondary particle is referred to as γ2, γ1 and γ2 satisfy the condition of Formula (II).       

       0.3≤γ1/γ2≤1.0  (II)

TECHNICAL FIELD

The present invention relates to a lithium-containing transition metalcomposite oxide, a positive electrode active material for a lithiumsecondary battery, a positive electrode for a lithium secondary battery,a lithium secondary battery, and a method for manufacturing alithium-containing transition metal composite oxide.

Priority is claimed on Japanese Patent Application No. 2017-230733,filed on Nov. 30, 2017, the content of which is incorporated herein byreference.

BACKGROUND ART

A lithium-containing transition metal composite oxide has been used as apositive electrode active material for a lithium secondary battery.Lithium secondary batteries have been already in practical use not onlyfor small power sources in mobile phone applications, notebook personalcomputer applications, and the like but also for medium-sized orlarge-sized power sources in automotive applications, power storageapplications, and the like.

In order to further expand the applications of lithium secondarybatteries, there is a demand for lithium secondary batteries havinghigher capacity and excellent output characteristics.

For the purpose of improving battery characteristics such as highcapacity and output characteristics, for example, Patent Literature 1describes a technique that focuses on the state of the surface ofsecondary particles of a lithium nickel composite oxide. In the methoddescribed in Patent Literature 1, a positive electrode active materialfor a lithium secondary battery in which an oxygen 1s spectrum and acarbon is spectrum of X-ray photoelectron spectroscopy (XPS) are inspecific ranges is described.

Patent Literature 2 defines the ratio of the number of lithium atoms tothe number of nickel atoms on the surface of a positive electrode activematerial and in the vicinity thereof.

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Unexamined Patent Application, FirstPublication No. 2004-327246

[Patent Literature 2] Japanese Unexamined Patent Application, FirstPublication No. 2016-115658

SUMMARY OF INVENTION Technical Problem

In order to further improve the output characteristics of the lithiumsecondary battery, the methods described in Patent Literatures 1 and 2have room for further improvement.

The present invention has been made in view of such circumstances, andan object thereof is to provide a lithium-containing transition metalcomposite oxide for a lithium secondary battery having good outputcharacteristics. Another object is to provide a positive electrodeactive material for a lithium secondary battery having thelithium-containing transition metal composite oxide, a positiveelectrode using the positive electrode active material for a lithiumsecondary battery, a lithium secondary battery, and a method formanufacturing a lithium-containing transition metal composite oxide.

Solution to Problem

The present invention includes the following [1] to [11].

[1] A lithium-containing transition metal composite oxide including:secondary particles that are aggregate of primary particles into or fromwhich lithium ions are dopable or dedopable, in which thelithium-containing transition metal composite oxide satisfies thefollowing conditions,

(1) the lithium-containing transition metal composite oxide isrepresented by Formula (I),

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0≤x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

(2) when an area value of a peak appearing at 53.8 eV in a lithium isspectrum is referred to as a and an area value of a peak appearing at529.0 eV in an oxygen is spectrum is referred to as β when X-rayphotoelectron spectroscopy is performed, and a ratio between α and β isreferred to as γ (α/β=γ),

γ is calculated for each of a surface of the secondary particle and aninside of the secondary particle, and when a γ value of the surface ofthe secondary particle is referred to as γ1 and a γ value of the insideof the secondary particle is referred to as γ2, γ1 and γ2 satisfy acondition of Formula (II).

0.3≤γ1/γ2≤1.0  (II)

[2] The lithium-containing transition metal composite oxide according to[1], in which an element ratio R (Li (Atom %)/O (Atom %)) calculatedfrom the peak appearing at 53.8 eV in the lithium Is spectrum and thepeak appearing at 529.0 eV in the oxygen 1s spectrum when the X-rayphotoelectron spectroscopy is performed is 0.4<R<0.8 in the inside ofthe secondary particle.

[3] The lithium-containing transition metal composite oxide according to[1] or [2], in which a BET specific surface area (m²/g) is 0.1 or moreand 3.0 or less.

[4] The lithium-containing transition metal composite oxide according toany one of [1] to [3], in which a crystallite size L₀₀₃ at a peak withina range of 2θ=18.7±1° in a powder X-ray diffraction measurement usingCuKα radiation is 400 Å or more and 1300 Å or less.

[5] The lithium-containing transition metal composite oxide according toany one of [1] to [4], in which a 50% cumulative volume particle sizeD₅₀ (μm) is 3 or more and 20 or less, and a difference between a maximumparticle diameter D_(max) and a minimum particle size D_(min) (μm) isD₅₀× 2/3 or more.

[6] The lithium-containing transition metal composite oxide according toany one of [1] to [5], in which, in Formula (I), 0<x≤0.2 is satisfied.

[7] A positive electrode active material for a lithium secondarybattery, including: the lithium-containing transition metal compositeoxide according to any one of [1] to [6].

[8] A positive electrode for a lithium secondary battery, including: thepositive electrode active material for a lithium secondary batteryaccording to [7].

[9] A lithium secondary battery including: the positive electrode for alithium secondary battery according to [8].

[10] A method for manufacturing a lithium-containing transition metalcomposite oxide including secondary particles that are aggregates ofprimary particles into or from which lithium ions are dopable ordedopable and represented by General Formula (I), the method including:a mixing step of mixing a lithium compound and a metal compositecompound containing at least nickel to obtain a mixture; a calciningstep of calcining the mixture to obtain a calcined product; and awashing step of washing the calcined product, in which, in the mixingstep, mixing is performed so that a molar ratio (Li/Me, a molar ratio oflithium to a total amount of metal elements excluding lithium) betweenlithium contained in the lithium compound and metal elements in themetal composite compound containing at least nickel exceeds 1, and inthe washing step, a temperature of a washing solution used for washingis set to −20° C. or higher and 40° C. or lower, and washing isperformed in an amount of the washing solution used for washing suchthat a concentration of lithium carbonate in the washing solution in acase where it is assumed that a total amount of residual lithiumcarbonate contained in the calcined product before washing is dissolvedin the washing solution is 1/10 or more and 3 or less times a solubilityof lithium carbonate in the washing solution at the temperature of thewashing solution during the washing step.

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0≤x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

[11] A method for manufacturing a lithium-containing transition metalcomposite oxide including secondary particles that are aggregates ofprimary particles into or from which lithium ions are dopable ordedopable and represented by General Formula (I), the method including:a mixing step of mixing a lithium compound and a metal compositecompound containing at least nickel to obtain a mixture; a calciningstep of calcining the mixture to obtain a calcined product; and awashing step of washing the calcined product, in which, in the mixingstep, mixing is performed so that a molar ratio (Li/Me, a molar ratio oflithium to a total amount of metal elements excluding lithium) betweenlithium contained in the lithium compound and metal elements in themetal composite compound containing at least nickel exceeds 1, and inthe washing step, a temperature of a slurry containing the calcinedproduct and a washing solution used for washing is maintained at −20° C.or higher and lower than 10° C., and washing is performed in an amountof the washing solution used for washing such that a concentration oflithium carbonate in the washing solution in a case where it is assumedthat a total amount of residual lithium carbonate contained in thecalcined product before washing is dissolved in the washing solution is1/10 or more and 3 or less times a solubility of lithium carbonate inthe washing solution at the temperature of the washing solution duringthe washing step.

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0<x<0.2, 0<y<0.5, 0<z<0.8, 0<w<0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

[12] A method for manufacturing a lithium-containing transition metalcomposite oxide, including secondary particles that are aggregates ofprimary particles into or from which lithium ions are dopable ordedopable and represented by General Formula (I), the method including:a mixing step of mixing a lithium compound and a metal compositecompound containing at least nickel to obtain a mixture; a calciningstep of calcining the mixture to obtain a calcined product; and awashing step of washing the calcined product, in which, in the mixingstep, mixing is performed so that a molar ratio (Li/Me, a molar ratio oflithium to a total amount of metal elements excluding lithium) betweenlithium contained in the lithium compound and metal elements in themetal composite compound containing at least nickel exceeds 1, and inthe washing step, a temperature of a washing solution used for washingis set to −20° C. or higher and 40° C. or lower, washing is performed inan amount of the washing solution used for washing such that aconcentration of lithium carbonate in the washing solution in a casewhere it is assumed that a total amount of residual lithium carbonatecontained in the calcined product before washing is dissolved in thewashing solution is 1/10 or more and 3 or less times a solubility oflithium carbonate in the washing solution at the temperature of thewashing solution during the washing step, and a temperature of a slurrycontaining the calcined product and the washing solution used forwashing is maintained at −20° C. or higher and lower than 10° C.

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0≤x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

Advantageous Effects of Invention

According to the present invention, it is possible to provide alithium-containing transition metal composite oxide for a lithiumsecondary battery having good output characteristics. In addition, it ispossible to provide a positive electrode active material for a lithiumsecondary battery having the lithium-containing transition metalcomposite oxide, a positive electrode using the positive electrodeactive material for a lithium secondary battery, a lithium secondarybattery, and a method for manufacturing a lithium-containing transitionmetal composite oxide.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic configuration view illustrating an example of alithium-ion secondary battery.

FIG. 1B is a schematic configuration view illustrating an example of thelithium-ion secondary battery.

FIG. 2 is a schematic view illustrating a definition of a surface of asecondary particle in the present embodiment.

FIG. 3 is a schematic view illustrating a definition of an inside of asecondary particle according to the present embodiment.

FIG. 4A is a schematic view describing a crystallite size in the presentinvention.

FIG. 4B is a schematic view describing a crystallite size in the presentinvention.

DESCRIPTION OF EMBODIMENTS <Lithium-Containing Transition MetalComposite Oxide>

A lithium-containing transition metal composite oxide of the presentembodiment includes secondary particles that are aggregates of primaryparticles into or from which lithium ions are dopable or dedopable. Thelithium-containing transition metal composite oxide of the presentembodiment satisfies the following requirements (1) and (2).Requirements (1) and (2) will be described.

<<Requirement (1)>>

The lithium-containing transition metal composite oxide of the presentembodiment is represented by Formula (I).

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0≤x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

From the viewpoint of obtaining a lithium secondary battery having highcycle characteristics, x in Formula (I) is preferably more than 0, morepreferably 0.01 or more, and even more preferably 0.02 or more. Inaddition, from the viewpoint of obtaining a lithium secondary batteryhaving higher initial Coulombic efficiency, x in Formula (I) ispreferably 0.1 or less, more preferably 0.08 or less, and even morepreferably 0.06 or less.

The upper limit and the lower limit of x can be arbitrarily combined.

For example, x is preferably more than 0 and 0.1 or less, morepreferably 0.01 or more and 0.08 or less, and even more preferably 0.02or more and 0.06 or less.

In the present specification, “having high cycle characteristics” meansthat the discharge capacity retention ratio is high.

In addition, from the viewpoint of obtaining a lithium secondary batteryhaving high cycle characteristics, γ in Formula (I) is preferably 0.005or more, more preferably 0.01 or more, and even more preferably 0.05 ormore. In addition, from the viewpoint of obtaining a lithium secondarybattery having high thermal stability, γ in Formula (I) is preferably0.4 or less, more preferably 0.35 or less, and even more preferably 0.33or less.

The upper limit and the lower limit of γ can be arbitrarily combined.

For example, γ is preferably 0.005 or more and 0.4 or less, morepreferably 0.01 or more and 0.35 or less, and even more preferably 0.05or more and 0.33 or less.

In addition, from the viewpoint of obtaining a lithium secondary batteryhaving high cycle characteristics, z in Formula (I) is preferably 0.01or more, and more preferably 0.03 or more. In addition, from theviewpoint of obtaining a lithium secondary battery having high storagecharacteristics at high temperatures (for example, in an environment at60° C.), z in Formula (I) is preferably 0.4 or less, more preferably0.38 or less, and even more preferably 0.35 or less.

The upper limit and the lower limit of z can be arbitrarily combined.

For example, z is preferably 0.01 or more and 0.4 or less, and morepreferably 0.03 or more and 0.38 or less.

In addition, from the viewpoint of obtaining a lithium secondary batteryhaving low battery resistance, w in Formula (I) is preferably more than0, more preferably 0.0005 or more, and even more preferably 0.001 ormore. In addition, from the viewpoint of obtaining a lithium secondarybattery having a high discharge capacity at a high current rate, w inFormula (I) is preferably 0.09 or less, more preferably 0.08 or less,and even more preferably 0.07 or less.

The upper limit and the lower limit of w can be arbitrarily combined.

For example, w is preferably more than 0 and 0.09 or less, morepreferably 0.0005 or more and 0.08 or less, and even more preferably0.001 or more and 0.07 or less.

In addition, from the viewpoint of obtaining a lithium secondary batteryhaving high cycle characteristics, M in Formula (I) is preferably one ormore metals selected from the group consisting of Ti, Mg, Al, W, B, andZr, and more preferably one or more metals selected from the groupconsisting of Al, W, B, and Zr.

<<Requirement (2)>>

The lithium-containing transition metal composite oxide of the presentembodiment satisfies Formula (II).

0.3≤γ1/γ2≤1.0  (II)

In Formula (II), γ1 and γ2 are values calculated by the followingmethod.

When the lithium-containing transition metal composite oxide issubjected to X-ray photoelectron spectroscopy, the area value of thepeak appearing at 53.8 eV in a lithium 1s spectrum is referred to as a,and the area value of the peak appearing at 529.0 eV in an oxygen 1sspectrum is referred to as β. The ratio between α and β is referred toas γ(α/β=γ).

For each of the surface of the secondary particles and the inside of thesecondary particles, γ is calculated. The γ value of the surface of thesecondary particles is referred to as γ1, and the γ value of the insideof the secondary particles is referred to as γ2.

Measurement of γ1

In the present embodiment, referring to FIG. 2, the “γ value (γ1) of thesurface of the secondary particle” is a value calculated when thesurface of secondary particles 33 of the lithium-containing transitionmetal composite oxide is subjected to X-ray photoelectron spectroscopy(XPS). That is, the γ value (γ1) is a value obtained by irradiating thesecondary particles with an X-ray indicated by reference numeral X andmeasuring photoelectrons 32 generated from the surface of the secondaryparticles. In the present invention, the surface of the secondaryparticles generally means a region with a depth of about 10 nm from thesurface of the secondary particles of the lithium-containing transitionmetal composite oxide toward the center. In a case where no peak appearsat a position of 53.8 eV in the lithium 1s spectrum or at a position of529.0 eV in the oxygen 1s spectrum due to the presence of impurities anda coating layer on the surface of the secondary particles of thelithium-containing transition metal composite oxide and γ1 cannot becalculated, the impurities and the coating layer on the surface of thesecondary particles of the lithium-containing transition metal compositeoxide may be removed by performing sputtering as appropriate. Thesputtering conditions may be appropriately adjusted so as to remove onlythe impurities and the coating layer on the surface of the secondaryparticles and not to remove the lithium-containing transition metalcomposite oxide present thereunder.

Measurement of γ2

Referring to FIG. 3, the “γ value (γ2) of the inside of the secondaryparticles” is a value calculated when the surface of secondary particles34 that had undergone a treatment to expose the inside thereof bysputtering of the secondary particles of the lithium-containingtransition metal composite oxide from the surface toward the centerportion is subjected to XPS. That is, the γ value (γ2) is a valueobtained by irradiating the secondary particles having the exposedinside with an X-ray indicated by reference numeral X and measuringphotoelectrons 32 generated from the surface of the secondary particles.In the present invention, regarding the inside of the secondaryparticles, a region in which the γ value does not change aftersufficient sputtering is referred to as the inside of the secondaryparticles, and the value in this case is referred to as γ2.

[Analysis of XPS in Depth Direction]

In order to calculate γ2, XPS measurement of the inside of the secondaryparticles is performed as follows. Inside an XPS apparatus, Ar ionsputtering is performed on the secondary particles under the sameconditions as those for sputtering to a depth of 10 nm when a SiO₂ filmis to be sputtered. Thereafter, XPS measurement is performed on theexposed region. Again, Ar ion sputtering is performed at the samelocation under the same conditions as those for sputtering to a depth of10 nm when the SiO₂ film is to be sputtered. Thereafter, the XPSmeasurement is performed again at the same point. This operation isrepeated, and the value when no change occurs in the γ value is referredto as γ2.

Measurement of α and β

The lithium-containing transition metal composite oxide is analyzed byXPS, and the area value a of the peak appearing at 53.8 eV in thelithium 1s spectrum and the area value β of the peak appearing at 529.0eV in the oxygen 1s spectrum are measured.

Then, the ratio γ (α/β) between α and β is calculated. Lithium containedin the lithium-containing transition metal composite oxide representedby Formula (I) has a peak at a position where the binding energy isabout 53.8 eV in XPS. That is, “53.8 eV” in the present specification issufficient if it can be determined that the peak is based on lithiumincluded in the lithium-containing transition metal composite oxideaccording to the present invention, and can be usually 53.8 eV±0.5 eV.

On the other hand, oxygen contained in the lithium-containing transitionmetal composite oxide represented by Formula (I) has a peak at aposition where the binding energy is about 529.0 eV in XPS. That is,“529.0 eV” in the present specification is sufficient if it can bedetermined that the peak is based on oxygen included in thelithium-containing transition metal composite oxide according to thepresent invention, and can be usually 529.0 eV±1 eV.

Lithium derived from lithium carbonate, lithium hydroxide, or lithiumoxide has a peak at a position where the binding energy is about 55.0 eVin XPS. That is, “55.0 eV” in the present specification is sufficient ifit can be determined that the peak is based on lithium included inlithium carbonate, lithium hydroxide, or lithium oxide, and can beusually 55.0 eV-0.5 eV.

In addition, oxygen derived from lithium carbonate, lithium hydroxide,and lithium oxide has a peak at a position where the binding energy isabout 531.1 eV in XPS. “531.1 eV” in the present specification issufficient if it can be determined that the peak is based on oxygenincluded in lithium carbonate, lithium hydroxide, or lithium oxide, andcan be usually 531.1 eV±1 eV. Therefore, the peak can be distinguishedfrom the peaks of lithium and oxygen contained in the lithium-containingtransition metal composite oxide.

Therefore, even in a case where lithium carbonate, lithium hydroxide, orlithium oxide and the lithium-containing transition metal compositeoxide are mixed, the area value a and the area value β can be calculatedby appropriately performing waveform separation by peak fitting.

In addition, as necessary, the area value a and the area value β can becalculated by performing waveform separation by peak fitting on thelithium 1s spectrum peak and the oxygen 1s spectrum peak obtained byXPS.

The ratio γ (α/β) between α and β represents the ratio of the peak areacorresponding to the number of lithium atoms contained in thelithium-containing transition metal composite oxide to the peak areacorresponding to the number of oxygen atoms of the lithium-containingtransition metal composite oxide. That is, the fact that γ is smallmeans that the ratio of lithium contained in the lithium-containingtransition metal composite oxide is small. That is, the fact that γ1 issmall means that the ratio of lithium contained in the surface of thesecondary particles of the lithium-containing transition metal compositeoxide is small. The fact that γ2 is small means that the ratio oflithium contained in the inside of the secondary particles of thelithium-containing transition metal composite oxide is small.

In the present embodiment, γ1/γ2 is 0.3 or more, preferably 0.5 or more,more preferably 0.6 or more, and particularly preferably 0.65 or more.In addition, γ1/γ2 is 1.0 or less, preferably 0.95 or less, morepreferably 0.9 or less, and particularly preferably 0.85 or less.

The upper limit and the lower limit thereof can be arbitrarily combined.

For example, γ1/γ2 is preferably 0.3 or more and 0.95 or less, morepreferably 0.5 or more and 0.95 or less, even more preferably 0.6 ormore and 0.9 or less, and particularly preferably 0.65 or more and 0.85or less.

The lithium-containing transition metal composite oxide of the presentembodiment that satisfies requirement (2) is characterized in that theconcentration gradient of lithium from the inside of the secondaryparticles to the surface of the secondary particles is small.

In the present embodiment, “concentration gradient” means that thelithium content in the lithium-containing transition metal compositeoxide decreases from the inside of the secondary particles toward thesurface of the secondary particles.

When the concentration gradient of lithium toward the surface of thesecondary particles is small, insertion and desorption of lithiumproceed efficiently, and a lithium secondary battery having excellentdischarge rate characteristics can be provided.

Contrary to this, in the lithium-containing transition metal compositeoxide having a large lithium concentration gradient toward the surfaceof the secondary particles, a region having a low lithium content isformed on the surface of the secondary particles. In this case, it ispresumed that the region having a low lithium content is a factor thathinders the insertion and desorption of lithium, and batterycharacteristics are considered to be inferior.

<<Element Ratio R (Li (Atom %)/O (Atom %))>>

In the lithium-containing transition metal composite oxide of thepresent embodiment, the element ratio R (Li (Atom %)/O (Atom %))calculated from the peak appearing at 53.8 eV in the lithium Is spectrumand the peak appearing at 529.0 eV in the oxygen 1s spectrum when X-rayphotoelectron spectroscopy is performed preferably satisfies 0.4≤R≤0.8in the inside of the secondary particles.

As necessary, by performing waveform separation by peak fitting on thelithium Is spectrum peak and the oxygen Is spectrum peak obtained byXPS, the peak areas of the peak appearing at 53.8 eV in the lithium 1sspectrum and the peak appearing at 529.0 eV in the oxygen Is spectrumcan be calculated. Furthermore, by multiplying each of the peak areas bya relative sensitivity factor, the values of Li (Atom %) and O (Atom %)are obtained, and the value of R can be calculated.

In the present embodiment, the element ratio R is more preferably 0.45or more, and particularly preferably 0.5 or more. In addition, theelement ratio R is more preferably 0.75 or less, and particularlypreferably 0.7 or less.

The upper limit and the lower limit thereof can be arbitrarily combined.

For example, the element ratio R is preferably 0.45 or more and 0.7 orless, and more preferably 0.5 or more and 0.7 or less.

When the element ratio R is within the above specific range, this meansthat the formation of lithium carbonate, lithium hydroxide, and lithiumoxide, which are factors that hinder the insertion and desorption oflithium into and from the secondary particles, is suppressed. When alarge amount of lithium carbonate, lithium hydroxide and lithium oxideare formed on the surface of the secondary particles, the peak derivedfrom the lithium-containing transition metal oxide during analysis byXPS becomes small, and the element ratio R deviates from the abovespecific range. That is, when the element ratio R is within the abovespecific range, it is possible to provide a lithium-containingtransition metal composite oxide for a lithium secondary battery inwhich a decrease in output characteristics is suppressed.

<<BET Specific Surface Area>>

In the present embodiment, from the viewpoint of obtaining a lithiumsecondary battery having a high discharge capacity at a high currentrate, the BET specific surface area (m²/g) of the lithium-containingtransition metal composite oxide is preferably 0.1 or more, preferably0.12 or more, and more preferably 0.15 or more. In addition, from theviewpoint of improving handling properties, the BET specific surfacearea is preferably 3 or less, more preferably 2.8 or less, and even morepreferably 2.5 or less.

The upper limit and the lower limit of the BET specific surface area(m²/g) can be arbitrarily combined. For example, the BET specificsurface area (m²/g) is preferably 0.1 or more and 3 or less, morepreferably 0.12 or more and 2.8 or less, even more preferably 0.15 ormore and 2.5 or less, and particularly preferably 0.1 or more and 2.0 orless.

In the measurement of the BET specific surface area, nitrogen gas isused as an adsorption gas. For example, the BET specific surface area isa value obtained by drying 1 g of a powder of a measurement object in anitrogen atmosphere at 105° C. for 30 minutes, and measuring the powderusing a BET specific surface area meter (for example, Macsorb(registered trademark) manufactured by MOUNTECH Co., Ltd.).

<<Crystallite Size>>

In the lithium-containing transition metal composite oxide of thepresent embodiment, it is preferable that a crystallite size L₀₀₃ (Å) ata peak (hereinafter, sometimes referred to as peak A) within a range of2θ=18.7±1° in powder X-ray diffraction measurement using CuKα radiationbe 400 or more and 1300 or less.

From the viewpoint of obtaining a lithium secondary battery having alarge charge capacity, the crystallite size L₀₀₃ (Å) is preferably 500or more, more preferably 550 or more, and even more preferably 600 ormore.

In addition, from the viewpoint of obtaining a lithium secondary batteryhaving high cycle characteristics, the crystallite size L₀₀₃ (Å) ispreferably 1000 or less, more preferably 900 or less, and even morepreferably 850 or less.

The upper limit and the lower limit of L₀₀₃ (Å) can be arbitrarilycombined.

For example, L₀₀₃ (Å) is preferably 500 or more and 1000 or less, morepreferably 550 or more and 900 or less, and even more preferably 600 ormore and 850 or less.

The crystallite size L₀₀₃ (Å) at the peak A of the lithium-containingtransition metal composite oxide of the present embodiment can beconfirmed as follows.

First, the lithium-containing transition metal composite oxide of thepresent embodiment is subjected to powder X-ray diffraction measurementusing CuKα as a radiation source in a diffraction angle 2θ measurementrange of 10° or more and 90° or less, and a peak corresponding to thepeak A is determined. Furthermore, the half-width of the determined peakis calculated, and the crystallite size can be calculated by using theScherrer equation L=Kλ/B cos θ (L: crystallite size, K: Scherrerconstant, X: X-ray wavelength B: peak half-width, θ: Bragg angle).Calculation of a crystallite size by the above equation is a methodhitherto used (for example, refer to “X-ray structure analysis-determinearrangement of atoms” issued Apr. 30, 2002, Third Edition, YoshioWaseda, Matsubara Eiichiro). Hereinafter, a case where a positiveelectrode active material for a lithium secondary battery has ahexagonal crystal structure belonging to the space group R-3m will bedescribed as an example in more detail with reference to the drawings.

FIG. 4A illustrates a schematic view of the 003 plane in a crystallite.In FIG. 4A, the crystallite size in a direction perpendicular to the 003plane corresponds to the crystallite size L₀₀₃ (Å) (FIG. 4B).

<<50% Cumulative Volume Particle Size>>

In terms of suppressing moisture adsorption, the 50% cumulative volumeparticle size D₅₀ (μm) of the lithium-containing transition metalcomposite oxide of the present embodiment is preferably 3 or more, morepreferably 5 or more, and particularly preferably 7 or more. Inaddition, in terms of improving handling properties, D₅₀ (μm) ispreferably 20 or less, more preferably 18 or less, and particularlypreferably 15 or less.

The upper limit and the lower limit of D₅₀ (μm) can be arbitrarilycombined.

For example, D₅₀ (μm) is preferably 3 or more and 20 or less, morepreferably 5 or more and 18 or less, and even more preferably 7 or moreand 15 or less.

D₅₀ (μm) of the lithium-containing transition metal composite oxide canbe measured, for example, as follows. 0.1 g of the powder of thelithium-containing transition metal composite oxide to be measured ispoured into 50 ml of 0.2 mass % sodium hexametaphosphate aqueoussolution to obtain a dispersion solution in which the powder isdispersed. The particle size distribution of the obtained dispersionsolution is measured using Mastersizer 2000 manufactured by MalvernInstruments Ltd. (laser diffraction scattering particle sizedistribution measuring device) to obtain a volume-based cumulativeparticle size distribution curve. In the obtained cumulative particlesize distribution curve, the volume particle size at a 50% cumulativepoint is referred to as the 50% cumulative volume particle size D₅₀ ofthe positive electrode active material for a lithium secondary battery.

In addition, in the obtained cumulative particle size distributioncurve, the maximum volume particle size is referred to as D_(max), andthe minimum volume particle size is referred to as D_(min).

Furthermore, in terms of enhancing processability during the productionof a positive electrode, the difference between the maximum particlediameter D_(max) and the minimum particle size D_(min)(μm) of thelithium-containing transition metal composite oxide of the presentembodiment is preferably D₅₀×2/3 or more.

<Method for Manufacturing Lithium-Containing Transition Metal CompositeOxide> <<Method 1 for Manufacturing Lithium-Containing Transition MetalComposite Oxide>>

A method 1 for manufacturing the lithium-containing transition metalcomposite oxide of the present invention (hereinafter, referred to as“manufacturing method 1”) includes a mixing step of mixing a lithiumcompound and a metal composite compound containing at least nickel toobtain a mixture, a calcining step of calcining the mixture to obtain acalcined product, and a washing step of washing the calcined product, asessential steps.

In the mixing step, mixing is performed so that the molar ratio (Li/Mc,the molar ratio of lithium to the total amount of metal elementsexcluding lithium) between lithium contained in the lithium compound andmetal elements in the metal composite compound containing at leastnickel exceeds 1.

In manufacturing method 1, in the washing step, the temperature of thewashing solution used for washing is set to −20° C. or higher and 40° C.or lower, and washing is performed in an amount of the washing solutionused for washing such that the concentration of lithium carbonate in thewashing solution in a case where it is assumed that the total amount ofresidual lithium carbonate contained in the calcined product beforewashing is dissolved in the washing solution is 1/10 or more and 3 orless times the saturated solubility of lithium carbonate in the washingsolution at the temperature of the washing solution.

In manufacturing the lithium-containing transition metal composite oxideof the present invention, it is preferable that, first, a metalcomposite compound including metals other than lithium, that is, Ni andCo which are essential metals, and at least one of Mn and M which areoptional metals (M is any one or more of Mg, Ca, Sr, Ba, Zn, B, Al, Ga,Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag,Cd, In, and Sn (that is, a metal composite compound containing nickel))be prepared, the metal composite compound be mixed with an appropriatelithium compound, and this mixture be calcined. The optional metal is ametal optionally contained in the metal composite compound as desired,and the optional metal may not be contained in the metal compositecompound in some cases. As the metal composite compound, a metalcomposite hydroxide or a metal composite oxide is preferable.Hereinafter, an example of the method for manufacturing thelithium-containing transition metal composite oxide will be described byseparately describing a step of manufacturing the metal compositecompound and a step of manufacturing the lithium-containing transitionmetal composite oxide.

(Step of Manufacturing Metal Composite Compound)

The metal composite compound can be produced by a generally known batchcoprecipitation method or continuous coprecipitation method.Hereinafter, the manufacturing method will be described in detail,taking a metal composite hydroxide, which is a metal composite compoundcontaining nickel, cobalt, manganese, and aluminum as metals, as anexample.

First, a nickel salt solution, a cobalt salt solution, a manganese saltsolution, an aluminum salt solution, and a complexing agent are reactedby a coprecipitation method, particularly a continuous method describedin Japanese Unexamined Patent Application, First Publication No.2002-201028, to manufacture a nickel cobalt manganese aluminum compositehydroxide.

A nickel salt which is a solute of the nickel salt solution is notparticularly limited, and for example, any of nickel sulfate, nickelnitrate, nickel chloride, and nickel acetate can be used. As a cobaltsalt which is a solute of the cobalt salt solution, for example, any ofcobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate canbe used. As a manganese salt which is a solute of the manganese saltsolution, for example, any of manganese sulfate, manganese nitrate,manganese chloride, and manganese acetate can be used. As aluminum whichis a solute of the aluminum salt solution, aluminum sulfate can be used.The above metal salts are used in proportions corresponding to thecomposition ratio of Formula (I). That is, the metal salts are used inproportions of nickel salt:cobalt salt:manganese salt:aluminumsalt=(1-γz-w):y:z:w. Also, water is used as a solvent.

The complexing agent is capable of forming a complex with ions ofnickel, cobalt, manganese, and aluminum in an aqueous solution, andexamples thereof include ammonium ion donors (ammonium hydroxide,ammonium sulfate, ammonium chloride, ammonium carbonate, ammoniumfluoride, and the like), hydrazine, ethylenediaminetetraacetic acid,nitrilotriacetic acid, uracildiacetic acid, and glycine. The complexingagent may not be contained, and in a case where the complexing agent iscontained, the amount of the complexing agent contained in the mixedsolution containing the nickel salt solution, the cobalt salt solution,the optional metal M salt solution, and the complexing agent is, forexample, more than 0 and 2.0 or less in terms of molar ratio to the sumof the number of moles of the metal salts.

During the precipitation, an alkali metal hydroxide (for example, sodiumhydroxide, or potassium hydroxide) is added, if necessary, in order toadjust the pH value of the aqueous solution.

The inside of a reaction tank is preferably an inert atmosphere. In thecase of the inert atmosphere, it is possible to suppress aggregation ofelements that are more easily oxidized than nickel, and to obtain auniform composite metal hydroxide.

In a case where manganese is contained as a transition metal, it ispreferable that the inside of the reaction tank be an appropriateoxygen-containing atmosphere or in the presence of an oxidizing agentwhile maintaining an inert atmosphere. This is because the morphology ofthe metal composite hydroxide can be easily controlled by appropriatelyoxidizing the transition metal. By controlling the state of the metalcomposite hydroxide, the element ratio R can be easily adjusted withinthe range of the present invention. The oxygen and the oxidizing agentin the oxygen-containing gas may have enough oxygen atoms to oxidize thetransition metal.

Unless a large amount of oxygen atoms are introduced, the inside of thereaction tank can be maintained in the inert atmosphere.

In order to cause the inside of the reaction tank to be in anoxygen-containing atmosphere, an oxygen-containing gas may be introducedinto the reaction tank. In order to improve the uniformity of thesolution in the reaction tank, it is more preferable to bubble theoxygen-containing gas. As the oxygen-containing gas, oxygen gas or air,or a mixed gas of oxygen gas or air and an oxygen-free gas such asnitrogen gas can be used. Among these, the mixed gas is preferable fromthe viewpoint of ease of adjustment of the oxygen concentration in thereaction tank. In addition, in order to promote the crystal growth ofthe metal composite hydroxide by oxidizing the transition metal elementwhile improving the uniformity in the reaction tank, it is preferable tostir the solution with a stirring blade installed in the reaction tank.By setting the stirring speed to 500 rpm or more and 1500 rpm or less, ametal composite hydroxide having an appropriately grown crystal can beobtained, and the adjustment of the element ratio R within the range ofthe present invention is facilitated.

In order to cause the inside of the reaction tank to be in the presenceof the oxidizing agent, an oxidizing agent may be added to the inside ofthe reaction tank. As the oxidizing agent, hydrogen peroxide, chlorate,hypochlorite, perchlorate, and permanganate can be used. Hydrogenperoxide is preferably used from the viewpoint of hardly bringingimpurities into the reaction system.

When the complexing agent in addition to the nickel salt solution, thecobalt salt solution, the manganese salt solution, and the aluminum saltsolution is continuously supplied to the reaction tank, nickel, cobalt,manganese, and aluminum react to manufacture a nickel cobalt manganesealuminum hydroxide. In order to cause requirement (2) and the elementratio R to be within the ranges of the present invention, thetemperature of the reaction tank is preferably controlled, for example,in a range of 20° C. or higher and 80° C. or lower, and preferably 30°C. or higher and 70° C. or lower during the reaction. Furthermore, inorder to cause requirement (2) and the element ratio R to be within theranges of the present invention, the pH value in the reaction tank ispreferably controlled, for example, in a range of a pH of 9 or more anda pH of 13 or less, and preferably a pH of 11 or more and a pH of 13 orless when the temperature of the solution in the reaction tank is 40° C.Under these conditions, the materials in the reaction tank areappropriately stirred. As the reaction tank, a reaction tank of a typewhich causes the formed reaction precipitate to overflow for separationcan be used.

By appropriately controlling the concentrations of the metal saltssupplied to the reaction tank, the stirring speed, the reactiontemperature, the reaction pH, calcining conditions, which will bedescribed later, and the like, it is possible to control variousphysical properties of a lithium-containing transition metal compositeoxide which is finally obtained, such as requirements (1) and (2),element ratio R, and BET specific surface area.

Since the reaction conditions depend on the size of the reaction tankused and the like, the reaction conditions may be optimized whilemonitoring various physical properties of the lithium composite oxidewhich is finally obtained.

After the above reaction, the obtained reaction precipitate is washedwith water and then dried to isolate a nickel cobalt manganese aluminumhydroxide as a nickel cobalt manganese aluminum composite compound. Inaddition, the obtained reaction precipitate may be washed with a weakacid water or an alkaline solution containing sodium hydroxide orpotassium hydroxide, as necessary.

In the present embodiment, from the viewpoint of controlling requirement(2), a metal composite compound isolated by washing a coprecipitateslurry with a washing solution containing an alkali and dehydrating theresultant is preferable.

As the washing solution containing an alkali, a sodium hydroxidesolution is preferable.

In the above example, the nickel cobalt manganese aluminum compositehydroxide is manufactured, but a nickel cobalt manganese aluminumcomposite oxide may be prepared. For example, a nickel cobalt manganesealuminum composite oxide can be prepared by calcining the nickel cobaltmanganese aluminum composite hydroxide. As the calcining time, the totaltime until the temperature is reached and the temperature retention isended after the start of temperature rising is preferably 1 hour orlonger and 30 hours or shorter. The temperature rising rate of a heatingstep in which the highest retention temperature is reached is preferably180° C./hr or more, more preferably 200° C./hr or more, and particularlypreferably 250° C./hr or more.

(Step of Manufacturing Lithium-Containing Transition Metal CompositeOxide) [Mixing Step]

The metal composite oxide or hydroxide is dried and thereafter mixedwith a lithium compound. The drying condition is not particularlylimited, and, for example, may be any of a condition under which a metalcomposite oxide or hydroxide is not oxidized and reduced (specifically,a condition under which oxides or hydroxides are dried), a conditionunder which a metal composite hydroxide is oxidized (specifically, adrying condition under which a hydroxide is oxidized to an oxide), and acondition under which a metal composite oxide is reduced (specifically,a drying condition under which an oxide is reduced to a hydroxide). Forconditions under which no oxidation and reduction occur, an inert gassuch as nitrogen, helium, or argon may be used, and for conditions underwhich a hydroxide is oxidized, oxygen or air may be used. In addition,as a condition under which a metal composite oxide is reduced, areducing agent such as hydrazine or sodium sulfite may be used in aninert gas atmosphere. As the lithium compound, any one or two or more oflithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide,lithium hydroxide hydrate, lithium oxide can be mixed and used.

After drying the metal composite oxide or hydroxide, classification maybe appropriately performed thereon. The lithium compound and metalcomposite hydroxide mentioned above are used in consideration of thecomposition ratio of the final object, and the lithium compound and thenickel cobalt manganese aluminum composite hydroxide are mixed inproportions such that the molar ratio (Li/Me) between lithium in thelithium compound and the metal elements in the nickel cobalt manganesealuminum composite hydroxide exceeds 1. That is, the lithium compoundand the nickel cobalt manganese aluminum composite hydroxide are mixedin proportions such that the molar ratio between lithium and the sum ofthe metal elements excluding lithium exceeds 1.

[Calcining Step]

For the calcining, dry air, oxygen atmosphere, inert atmosphere, or thelike is used depending on the desired composition, and a plurality ofheating steps are performed as necessary.

The calcining temperature of the metal composite oxide or hydroxide andthe lithium compound such as lithium hydroxide or lithium carbonate isnot particularly limited, but is preferably 600° C. or higher and 1000°C. or lower, more preferably 680° C. or higher and 950° C. or lower, andeven more preferably 700° C. or higher and 900° C. or lower.

When the calcining temperature is equal to or higher than the lowerlimit, a positive electrode active material for a lithium secondarybattery having a strong crystal structure can be obtained. When thecalcining temperature is equal to or lower than the upper limit,volatilization of lithium on the surface of the secondary particles canbe reduced.

The calcining temperature in the present specification means thetemperature of the atmosphere in a calcining furnace, and is the highesttemperature of the retention temperature in a main calcining step(hereinafter, sometimes referred to as the highest retentiontemperature). In the case of the main calcining step having a pluralityof heating steps, the calcining temperature means the temperature whenheating is performed at the highest retention temperature among theheating steps.

The calcining time is preferably 3 hours or longer and 50 hours orshorter. When the calcining time exceeds 50 hours, the batteryperformance tends to be inferior due to volatilization of lithium. Whenthe calcining time is shorter than 3 hours, the crystals develop poorly,and the battery performance tends to be deteriorated. In addition, it isalso effective to perform preliminary calcining before theabove-mentioned calcining. The preliminary calcining is preferablyperformed in a temperature range of 300° C. or higher and 850° C. orlower for 1 hour or longer and 10 hours or shorter.

In the present embodiment, the temperature rising rate of the heatingstep in which the highest retention temperature is reached is preferably180° C./hr or more, more preferably 200° C./hr or more, and particularlypreferably 250° C./hr or more.

The temperature rising rate of the heating step in which the highestretention temperature is reached is calculated from the time from whenthe temperature rising is started until a retention temperature, whichwill be described, is reached in a calcining apparatus.

The calcined product contains impurities in addition to thelithium-containing transition metal composite oxide. In the presentembodiment, “impurities” include sulfur-containing compounds (residualsulfate radicals) such as SO₄ remaining on the surface of the particlesof the lithium-containing transition metal composite oxide after thecalcining step, residual lithium carbonate, coprecipitation residues ofalkali metals used for pH control, and the like.

In a case where a sulfate is used as a transition metal, there are caseswhere sulfate radicals resulting therefrom remain. In the presentembodiment, the source of the residual sulfate radicals as theimpurities is not particularly limited. For example, even in a casewhere a sulfate is not used, sulfur-containing compounds remaining onthe surface of the particles due to various materials used and the likeare also included in the impurities.

Furthermore, in a case where lithium carbonate is used as a lithiumsource, lithium carbonate as an impurity includes residual lithiumcarbonate resulting therefrom. Even in a case where a lithium sourceother than lithium carbonate is used, lithium carbonate that can begenerated by reaction with carbon dioxide in the air is also included inthe “impurities”.

The lithium-containing transition metal composite oxide obtained by thecalcining is appropriately classified after pulverization. Thepulverization of the lithium-containing transition metal composite oxideis preferably pulverization with a strength that breaks the aggregationof the secondary particles and does not crush the secondary particlesthemselves.

[Washing Step]

In the washing step, the washing solution and the calcined product (thatis, the calcined lithium-containing transition metal composite oxide)are mixed to form a slurry, and the slurry is stirred for apredetermined time and then filtered to wash the calcined productpowder. By performing the washing step, impurities contained in thecalcined product obtained in the calcining step can be removed. In thiscase, from the viewpoint of suppressing excessive elution of lithiumfrom the lithium-containing transition metal composite oxide inside theparticles as the calcined product powder, the amount of the washingsolution for the calcined product is adjusted to a washing solutionamount such that the concentration of lithium carbonate in the washingsolution in a case where it is assumed that the total amount of residuallithium carbonate contained in the calcined product before washing isdissolved in the washing solution is 1/10 or more times the solubility(the solute concentration in the saturated solution) of lithiumcarbonate in the washing solution at the temperature of the washingsolution during the washing step. The washing solution amount isadjusted such that the concentration of lithium carbonate in the washingsolution is preferably ⅕ or more times, more preferably 1/3 or moretimes, and even more preferably 1/2 or more times the solubility oflithium carbonate in the washing solution at the temperature of thewashing solution during the washing step. In addition, from theviewpoint of having sufficient handling properties, the washing solutionamount is adjusted such that the concentration of lithium carbonate inthe washing solution in a case where it is assumed that the total amountof residual lithium carbonate contained in the calcined product beforewashing is dissolved in the washing solution is 3 or less times thesolubility of lithium carbonate in the washing solution at thetemperature of the washing solution during the washing step. The washingsolution amount is adjusted such that the concentration of lithiumcarbonate in the washing solution is preferably 2 or less times, andmore preferably 1 or less times the solubility of lithium carbonate inthe washing solution at the temperature of the washing solution duringthe washing step.

The upper limit and the lower limit of the washing solution amount canbe arbitrarily combined. For example, the washing solution amount isadjusted such that the concentration of lithium carbonate in the washingsolution is preferably 1/10 or more times and 3 or less times,preferably ⅕ or more times and 2 or less times, more preferably 1/3 ormore times and 1 or less times, and even more preferably 1/2 or moretimes and 1 or less times the solubility of lithium carbonate in thewashing solution at the temperature of the washing solution during thewashing step.

When lithium is excessively eluted from the lithium-containingtransition metal composite oxide inside the particles as the calcinedproduct powder by the washing step, Li/Me of the lithium-containingtransition metal composite oxide, that is, the molar ratio of lithium(the molar ratio of lithium to the total amount (total molar quantity)of the metal elements excluding lithium) decreases. However, byadjusting the washing solution amount, a decrease in Li/Me can besuppressed.

Examples of the washing solution used in the washing step include waterand an alkaline solution. In the present embodiment, water ispreferable.

The washing time is not particularly limited, but is preferably 1 minuteor longer, and more preferably 5 minutes or longer from the viewpoint ofsufficiently removing impurities. In addition, from the viewpoint ofenhancing productivity, the washing time is preferably 120 minutes orshorter, and more preferably 60 minutes or shorter.

In the washing step of manufacturing method 1, the temperature of thewashing solution used is from −20° C. or higher and 40° C. or lower.From the viewpoint of suppressing excessive elution of lithium from thelithium-containing transition metal composite oxide inside the calcinedproduct powder during the washing, the temperature of the washingsolution used is preferably 25° C. or lower, more preferably 15° C. orlower, and particularly preferably lower than 10° C. From the viewpointof preventing freezing of the washing solution, the temperature of thewashing solution used is more preferably −10° C. or higher, even morepreferably −5° C. or higher, and particularly preferably 0° C. orhigher. The upper limit and the lower limit thereof can be arbitrarilycombined. For example, the temperature of the washing solution ispreferably −10° C. or higher and 25° C. or lower, more preferably −5° C.or higher and 15° C. or lower, and particularly preferably 0° C. orhigher and lower than 10° C. Particularly, by causing the temperature ofthe washing solution to be 0° C. or higher and lower than 10° C., theimpurities of the obtained lithium-containing transition metal compositeoxide can be sufficiently removed, excessive elution of lithium from thesurface of the secondary particles of the obtained lithium-containingtransition metal composite oxide can be suppressed, and theconcentration gradient can be controlled to be small so as to satisfyFormula (II). Accordingly, a lithium-containing transition metalcomposite oxide having a high output at a high voltage and a highcurrent rate can be obtained.

[Drying Step]

In the present embodiment, it is preferable that a drying step befurther included after the washing step. That is, it is preferable thatthe mixing step, the calcining step, the washing step, and the dryingstep be included in this order. The temperature and method for dryingthe lithium-containing transition metal composite oxide in the dryingstep are not particularly limited, but the drying temperature ispreferably 30° C. or higher, more preferably 40° C. or higher, and evenmore preferably 50° C. or higher from the viewpoint of sufficientlyremoving moisture. In addition, from the viewpoint of preventing theformation of a heterophase on the surface, the drying temperature ispreferably lower than 300° C., more preferably 250° C. or lower, andeven more preferably 200° C. or lower. The upper limit and the lowerlimit of the drying temperature can be arbitrarily combined. Forexample, the drying temperature is preferably 30° C. or higher and lowerthan 300° C., more preferably 40° C. or higher and 250° C. or lower, andeven more preferably 50° C. or higher and 200° C. or lower.

The atmosphere in the drying step includes an oxygen atmosphere, aninert atmosphere, a reduced pressure atmosphere, and a vacuumatmosphere. By performing the heat treatment after the washing in theabove atmosphere, the reaction between the lithium-containing transitionmetal composite oxide and moisture or carbon dioxide in the atmosphereduring the heat treatment is suppressed, and a lithium-containingtransition metal composite oxide with fewer impurities is obtained.

[Re-Calcining Step]

In the present embodiment, a re-calcining step may be further includedafter the washing step. That is, the mixing step, the calcining step,the washing step, and the re-calcining step may be included in thisorder.

The calcining temperature in the re-calcining step of thelithium-containing metal composite oxide is not particularly limited,but is preferably 300° C. or higher, more preferably 350° C. or higher,and even more preferably 400° C. or higher from the viewpoint ofpreventing a reduction in charge capacity. In addition, although thereis no particular limitation, the calcining temperature is preferably1000° C. or lower, and more preferably 950° C. or lower from theviewpoint of preventing volatilization of lithium and obtaining alithium-containing transition metal composite oxide having a targetcomposition.

The volatilization of lithium can be controlled by the calciningtemperature.

The upper limit and the lower limit of the calcining temperature can bearbitrarily combined. For example, the calcining temperature ispreferably 1000° C. or lower and 300° C. or higher, more preferably 950°C. or lower and 350° C. or higher, and even more preferably 950° C. orlower and 400° C. or higher.

As the re-calcining time, the total time until the temperature isreached and the temperature retention is ended after the start oftemperature rising is preferably 1 hour or longer and 30 hours orshorter. When the total time is 30 hours or shorter, volatilization oflithium can be suppressed, and deterioration of the battery performancecan be prevented.

When the total time is 1 hour or longer, the development of crystalsproceeds favorably, and the battery performance can be improved.

In addition, it is also effective to perform preliminary calciningbefore the above-mentioned calcining. The preliminary calcining asdescribed above is preferably performed in a temperature range of 300°C. or higher and 850° C. or lower for 1 hour or longer and 10 hours orshorter.

In the present embodiment, the temperature rising rate of the heatingstep in which the highest retention temperature is reached is preferably180° C./hr or more, more preferably 200° C./hr or more, and particularlypreferably 250° C./hr or more.

By performing the re-calcining step under the above conditions,impurities can be reduced.

[Method for Manufacturing Positive Electrode Active Material for LithiumSecondary Battery Having Coating Particles or Coating Layer]

In the case of manufacturing a positive electrode active material for alithium secondary battery having coating particles or a coating layer, acoating raw material and the lithium-containing transition metalcomposite oxide are first mixed. Thereafter, by performing a heattreatment as necessary, coating particles or a coating layer made of thecoating raw material can be formed on the surface of primary particlesor secondary particles of the lithium-containing transition metalcomposite oxide.

As the coating raw material, an oxide, hydroxide, carbonate, nitrate,sulfate, halide, oxalate, or alkoxide of one or more elements selectedfrom the group consisting of aluminum, boron, titanium, zirconium, andtungsten can be used, and an oxide is preferable. As the coating rawmaterial, aluminum oxide, aluminum hydroxide, aluminum sulfate, aluminumchloride, aluminum alkoxide, boron oxide, boric acid, titanium oxide,titanium chloride, titanium alkoxide, zirconium oxide, tungsten oxide,and tungstic acid can be adopted, and aluminum oxide, aluminumhydroxide, boron oxide, boric acid, zirconium oxide, and tungsten oxideare preferable.

The coating raw material is preferably finer than the secondary particleof the lithium-containing transition metal composite oxide. Accordingly,the surface of the lithium-containing transition metal composite oxidecan be more efficiently coated with the coating raw material.Specifically, the average secondary particle diameter of the coating rawmaterial is preferably 1 μm or less, and more preferably 0.1 μm or less.

The lower limit of the average secondary particle diameter of thecoating raw material is preferably as small as possible, and forexample, is 0.001 μm. The average secondary particle diameter of thecoating raw material can be measured in the same manner as the averagesecondary particle diameter of the lithium-containing transition metalcomposite oxide.

The mixing of the coating raw material and the lithium-containingtransition metal composite oxide may be performed in the same manner asthe mixing during the manufacturing of the positive electrode activematerial for a lithium secondary battery. A method of mixing using amixing apparatus that does not include mixing media such as balls anddoes not involve strong pulverization, such as a method of mixing usinga powder mixer equipped with a stirring blade inside, is preferable.Furthermore, the coating layer can be more firmly attached to thesurface of the lithium-containing transition metal composite oxide bybeing held in an atmosphere containing water after mixing.

The heat treatment conditions (temperature, retention time) in the heattreatment performed as necessary after the mixing of the coating rawmaterial and the lithium-containing transition metal composite oxide mayvary depending on the kind of the coating raw material. The heattreatment temperature is preferably set to be in a range of 300° C. orhigher and 850° C. or lower, but is preferably a temperature equal to orlower than the calcining temperature of the lithium-containingtransition metal composite oxide. When the temperature is higher thanthe calcining temperature of the lithium-containing transition metalcomposite oxide, there are cases where the coating raw material forms asolid solution with the lithium-containing transition metal compositeoxide and the coating layer is not formed. The retention time in theheat treatment is preferably set to be shorter than the retention timeat the time of calcining. As an atmosphere in the heat treatment, anatmosphere gas similar to that in the above-described calcining can beadopted.

A positive electrode active material for a lithium secondary battery canbe obtained by forming the coating layer on the surface of thelithium-containing transition metal composite oxide using a techniquesuch as sputtering, CVD, or vapor deposition.

Moreover, there are cases where a positive electrode active material fora lithium secondary battery having a coating layer is obtained by mixingand calcining the metal composite oxide or hydroxide, the lithiumcompound, and the coating raw material.

The positive electrode active material for a lithium secondary batteryprovided with the coating layer on the surface of the primary particlesor secondary particles of the lithium-containing transition metalcomposite oxide is appropriately crushed and classified to be a positiveelectrode active material for a lithium secondary battery having acoating layer.

<<Method 2 for Manufacturing Lithium-Containing Transition MetalComposite Oxide>>

A method 2 for manufacturing the lithium-containing transition metalcomposite oxide of the present invention (hereinafter, referred to as“manufacturing method 2”) includes a mixing step of mixing a lithiumcompound and a metal composite compound containing at least nickel toobtain a mixture, a calcining step of calcining the mixture to obtain acalcined product, and a washing step of washing the calcined product, asessential steps.

In the mixing step, mixing is performed so that the molar ratio (Li/Me)between lithium contained in the lithium compound and metal element inthe metal composite compound containing at least nickel exceeds 1.

Manufacturing method 2 of the present invention includes the same stepsas those of manufacturing method 1 of the present invention except thatthe washing step is different. Description regarding (Step ofManufacturing Metal Composite Compound) and (Step of ManufacturingLithium-Containing Transition Metal Composite Compound) that may beincluded in manufacturing method 2, and furthermore, [Mixing Step] and[Calcining Step] which are essential steps of manufacturing method 2,[Drying Step] and [Re-calcining Step] of optional steps, and [PositiveElectrode Active Material for Lithium Secondary Battery Having CoatingParticles or Coating Layer] are the same as those of manufacturingmethod 1.

Hereinafter, the washing step of manufacturing method 2 will bedescribed.

[Washing Step]

In the washing step, the washing solution and the calcined product (thatis, the calcined lithium-containing transition metal composite oxide)are mixed to form a slurry, and the slurry is stirred for apredetermined time and then filtered to wash the calcined productpowder. By performing the washing step, impurities contained in thecalcined product obtained in the calcining step can be removed. In thiscase, from the viewpoint of suppressing excessive elution of lithiumfrom the lithium-containing transition metal composite oxide inside theparticles as the calcined product powder, the amount of the washingsolution for the calcined product is adjusted to a washing solutionamount such that the concentration of lithium carbonate in the washingsolution in a case where it is assumed that the total amount of residuallithium carbonate contained in the calcined product before washing isdissolved in the washing solution is 1/10 or more times the solubilityof lithium carbonate in the washing solution at the temperature of thewashing solution during the washing step. The washing solution amount isadjusted such that the concentration of lithium carbonate in the washingsolution is preferably ⅕ or more times, and more preferably 1/3 or moretimes the solubility of lithium carbonate in the washing solution at thetemperature of the washing solution. In addition, from the viewpoint ofhaving sufficient handling properties, the washing solution amount isadjusted such that the concentration of lithium carbonate in the washingsolution in a case where it is assumed that the total amount of residuallithium carbonate contained in the calcined product before washing isdissolved in the washing solution is 3 or less times the solubility oflithium carbonate in the washing solution at the temperature of thewashing solution during the washing step. The washing solution amount isadjusted such that the concentration of lithium carbonate in the washingsolution is preferably 2 or less times, and more preferably 1 or lesstimes the solubility of lithium carbonate in the washing solution at thetemperature of the washing solution.

The upper limit and the lower limit of the washing solution amount canbe arbitrarily combined. For example, the washing solution amount isadjusted such that the concentration of lithium carbonate in the washingsolution is preferably 1/10 or more times and 3 or less times,preferably ⅕ or more times and 2 or less times, and more preferably 1/3or more times and 1 or less times the solubility of lithium carbonate inthe washing solution at the temperature of the washing solution duringthe washing step.

When lithium is excessively eluted from the lithium-containingtransition metal composite oxide inside the particles as the calcinedproduct powder by the washing step, Li/Me of the lithium nickelcomposite oxide, that is, the molar ratio of lithium (the molar ratio oflithium to the total amount of the metal elements excluding lithium)decreases.

However, by adjusting the washing solution amount, a decrease in Li/Mecan be suppressed.

Examples of the washing solution used in the washing step include waterand an alkaline solution. In the present embodiment, water ispreferable.

The washing time is not particularly limited, but is preferably 1 minuteor longer, and more preferably 5 minutes or longer from the viewpoint ofsufficiently removing impurities. In addition, from the viewpoint ofenhancing productivity, the washing time is preferably 120 minutes orshorter, and more preferably 60 minutes or shorter.

In manufacturing method 2, in the washing step, the temperature of theslurry containing the calcined product and the washing solution used forwashing is maintained at −20° C. or higher and lower than 10° C., andwashing is performed in an amount of the washing solution in a casewhere it is assumed that the total amount of residual lithium carbonatecontained in the calcined product before washing is dissolved in thewashing solution such that the concentration of lithium carbonate in thewashing solution is 1/10 or more times and 3 or less times thesolubility of lithium carbonate in the washing solution at thetemperature of the slurry.

In the washing step in manufacturing method 2, the temperature of theslurry containing the calcined product and the washing solution used forwashing is maintained at −20° C. or higher and lower than 10° C. Fromthe viewpoint of suppressing excessive elution of lithium from thelithium-containing transition metal composite oxide inside the particlesas the calcined product powder during the washing, the temperature ofthe slurry is more preferably 8° C. or lower, even more preferably 7° C.or lower, and particularly preferably is 6° C. or lower. From theviewpoint of preventing freezing of the washing solution, thetemperature of the slurry is preferably −10° C. or higher, morepreferably −5° C. or higher, and particularly preferably 0° C. orhigher. The upper limit and the lower limit of the temperature of theslurry can be arbitrarily combined.

For example, the temperature of the slurry is preferably −10° C. orhigher and 8° C. or lower, more preferably −5° C. or higher and 7° C. orlower, and even more preferably 0° C. or higher and 6° C. or lower.

By causing the temperature of the slurry to be within the above range,the impurities of the obtained lithium-containing transition metalcomposite oxide can be sufficiently removed, excessive elution oflithium from the surface of the secondary particles of the obtainedlithium-containing transition metal composite oxide can be suppressed,and the lithium concentration gradient can be controlled to be small soas to satisfy Formula (II). Accordingly, a lithium nickel metalcomposite oxide for a lithium secondary battery having a high output ata high voltage and a high current rate can be obtained.

In the present specification, maintaining the temperature of the slurryat the above-mentioned temperature means that the temperature reaches aspecified temperature before the washing step is ended. For example,after mixing the washing solution and the calcined product, thetemperature of the slurry may be maintained within the above-mentionedtemperature range until 1 minute before the washing step is ended.

<<Method 3 for Manufacturing Lithium-Containing Transition MetalComposite Oxide>>

A method 3 for manufacturing the lithium-containing transition metalcomposite oxide of the present invention (hereinafter, referred to as“manufacturing method 3”) includes a mixing step of mixing a lithiumcompound and a metal composite compound containing at least nickel toobtain a mixture, a calcining step of calcining the mixture to obtain acalcined product, and a washing step of washing the calcined product, asessential steps.

In the mixing step, mixing is performed so that the molar ratio (Li/Me)between lithium contained in the lithium compound and metal element inthe metal composite compound containing at least nickel exceeds 1.

Manufacturing method 3 of the present invention includes the same stepsas those of manufacturing method 1 of the present invention except thatthe washing step is different. Description regarding (Step ofManufacturing Metal Composite Compound) and (Step of ManufacturingLithium-Containing Transition Metal Composite Compound) that may beincluded in manufacturing method 3, and furthermore, [Mixing Step] and[Calcining Step] which are essential steps of manufacturing method 3,[Drying Step] and [Re-calcining Step] of optional steps, and [PositiveElectrode Active Material for Lithium Secondary Battery Having CoatingParticles or Coating Layer] are the same as those of manufacturingmethod 1.

Hereinafter, the washing step of manufacturing method 3 will bedescribed.

The washing step of manufacturing method 3 satisfies all of thefollowing requirements (A), (B), and (C).

(A) The temperature of the washing solution used for washing is set to−20° C. or higher and 40° C. or lower.

(B) Washing is performed in an amount of the washing solution used forwashing such that the concentration of lithium carbonate in the washingsolution in a case where it is assumed that the total amount of residuallithium carbonate contained in the calcined product before washing isdissolved in the washing solution is 1/10 or more times and 3 or lesstimes the solubility of lithium carbonate in the washing solution at thetemperature of the washing solution during the washing step.

(C) The temperature of the slurry containing the calcined product andthe washing solution used for washing is maintained at −20° C. or higherand lower than 10° C.

Description regarding the requirements (Å) and (B) in manufacturingmethod 3 is the same as the description regarding the washing stepdescribed in manufacturing method 1. Description regarding requirement(C) in manufacturing method 3 is the same as the description of thewashing step described in manufacturing method 2.

In manufacturing method 3, by causing the washing step to satisfy all ofthe requirements (A) to (C), the impurities of the obtainedlithium-containing transition metal composite oxide can be sufficientlyremoved, excessive elution of lithium from the surface of the secondaryparticles of the obtained lithium-containing transition metal compositeoxide can be suppressed, and the lithium concentration gradient can becontrolled to be small so as to satisfy Formula (II). Accordingly, alithium-containing transition metal composite oxide having a high outputat a high voltage and a high current rate can be obtained.

In manufacturing method 3, it is more preferable that the temperature ofthe washing solution used for the washing of requirement (A) be 0° C. orhigher and 20° C. or lower, and the temperature of the slurry ofrequirement (C) be 0° C. or higher and 10° C. or lower.

There are cases where the lithium-containing transition metal compositeoxide according to one embodiment of the present invention is obtainedwithout a washing step. For example, a lithium-containing transitionmetal composite oxide that satisfies the conditions (1) and (2) isobtained by obtaining a metal composite hydroxide as the metal compositecompound described in the manufacturing methods 1 to 3, thereaftercalcining the metal composite hydroxide under the condition of 700° C.or higher and 900° C. or lower, and 1 hour or longer and 30 hours orshorter to obtain a metal composite oxide, mixing the metal compositeoxide with a lithium compound, and calcining the mixture under thecondition of 700° C. or higher and 900° C. or lower, and 3 hours orlonger and 50 hours or shorter.

<Lithium Secondary Battery>

Next, a positive electrode using the lithium-containing transition metalcomposite oxide of the present embodiment as a positive electrode activematerial of a lithium secondary battery, and a lithium secondary batteryhaving the positive electrode will be described while describing theconfiguration of a lithium secondary battery.

An example of the lithium secondary battery of the present embodimentincludes a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolytic solution disposed between the positive electrode andthe negative electrode.

FIGS. 1A and 1B are schematic views illustrating an example of thelithium secondary battery of the present embodiment. A cylindricallithium secondary battery 10 of the present embodiment is manufacturedas follows.

First, as illustrated in FIG. 1A, a pair of separators 1 having a stripshape, a strip-shaped positive electrode 2 having a positive electrodelead 21 at one end, and a strip-like negative electrode 3 having anegative electrode lead 31 at one end are stacked in order of theseparator 1, the positive electrode 2, the separator 1, and the negativeelectrode 3 and are wound to form an electrode group 4.

Next, as shown in FIG. 1B, the electrode group 4 and an insulator (notillustrated) are accommodated in a battery can 5, the can bottom is thensealed, the electrode group 4 is impregnated with an electrolyticsolution 6, and an electrolyte is disposed between the positiveelectrode 2 and the negative electrode 3. Furthermore, the upper portionof the battery can 5 is sealed with a top insulator 7 and a sealing body8, whereby the lithium secondary battery 10 can be manufactured.

The shape of the electrode group 4 is, for example, a columnar shapesuch that the cross-sectional shape when the electrode group 4 is cut ina direction perpendicular to the winding axis is a circle, an ellipse, arectangle, or a rectangle with rounded corners.

In addition, as a shape of the lithium secondary battery having theelectrode group 4, a shape defined by IEC60086 which is a standard for abattery defined by the International Electrotechnical Commission (TEC),or by JIS C 8500 can be adopted. For example, shapes such as acylindrical shape and a square shape can be adopted.

Furthermore, the lithium secondary battery is not limited to the woundtype configuration, and may have a stacked type configuration in which astacked structure of a positive electrode, a separator, a negativeelectrode, and a separator is repeatedly stacked. The stacked typelithium secondary battery can be exemplified by a so-called coin typebattery, a button type battery, and a paper type (or sheet type)battery.

Hereinafter, each configuration will be described in order.

(Positive Electrode)

The positive electrode of the present embodiment can be manufactured byfirst adjusting a positive electrode mixture containing a positiveelectrode active material, a conductive material, and a binder, andcausing a positive electrode current collector to hold the positiveelectrode mixture.

(Conductive Material)

A carbon material can be used as the conductive material included in thepositive electrode of the present embodiment. As the carbon material,there are graphite powder, carbon black (for example, acetylene black),a fibrous carbon material, and the like. Since carbon black is fineparticles and has a large surface area, the addition of a small amountof carbon black to the positive electrode mixture increases theconductivity inside the positive electrode and thus improve the chargeand discharge efficiency and output characteristics. However, when thecarbon black is added too much, both the binding force between thepositive electrode mixture and the positive electrode current collectorand the binding force inside the positive electrode mixture by thebinder decrease, which causes an increase in internal resistance.

The proportion of the conductive material in the positive electrodemixture is preferably 5 parts by mass or more and 20 parts by mass orless with respect to 100 parts by mass of the positive electrode activematerial. In a case of using a fibrous carbon material such asgraphitized carbon fiber or carbon nanotube as the conductive material,the proportion can be reduced. The ratio of the positive electrodeactive material to the total mass of the positive electrode mixture ispreferably 80 to 98 mass %.

(Binder)

A thermoplastic resin can be used as the binder included in the positiveelectrode of the present embodiment.

As the thermoplastic resin, fluorine resins such as polyvinylidenefluoride (hereinafter, sometimes referred to as PVDF),polytetrafluoroethylene (hereinafter, sometimes referred to as PTFE),tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers,hexafluoropropylene-vinylidene fluoride copolymers, andtetrafluoroethylene-perfluorovinyl ether copolymers; and polyolefinresins such as polyethylene and polypropylene can be adopted.

These thermoplastic resins may be used as a mixture of two or more. Byusing a fluorine resin and a polyolefin resin as the binder and settingthe ratio of the fluorine resin to the entire positive electrode mixtureto 1 mass % or more and 10 mass % or less and the ratio of the fluorineresin to 0.1 mass % or more and 2 mass % or less, a positive electrodemixture having both high adhesion to the positive electrode currentcollector and high bonding strength in the positive electrode mixturecan be obtained.

(Positive Electrode Current Collector)

As the positive electrode current collector included in the positiveelectrode of the present embodiment, a strip-shaped member formed of ametal material such as Al, Ni, or stainless steel as the formingmaterial can be used. Among these, from the viewpoint of easy processingand low cost, it is preferable to use Al as the forming material andprocess Al into a thin film.

As a method of causing the positive electrode current collector to holdthe positive electrode mixture, a method of press-forming the positiveelectrode mixture on the positive electrode current collector can beadopted. In addition, the positive electrode mixture may be held by thepositive electrode current collector by forming the positive electrodemixture into a paste using an organic solvent, applying the paste of thepositive electrode mixture to at least one side of the positiveelectrode current collector, drying the paste, and pressing the paste tobe fixed.

In a case of forming the positive electrode mixture into a paste, as theorganic solvent which can be used, amine solvents such asN,N-dimethylaminopropylamine and diethylenetriamine; ether solvents suchas tetrahydrofuran; ketone solvents such as methyl ethyl ketone; estersolvents such as methyl acetate; and amide solvents such asdimethylacetamide and N-methyl-2-pyrrolidone (hereinafter, sometimesreferred to as NMP) can be adopted.

Examples of a method of applying the paste of the positive electrodemixture to the positive electrode current collector include a slit diecoating method, a screen coating method, a curtain coating method, aknife coating method, a gravure coating method, and an electrostaticspraying method.

The positive electrode can be manufactured by the method mentionedabove.

(Negative Electrode)

The negative electrode included in the lithium secondary battery of thepresent embodiment may be capable of being doped with or dedoped fromlithium ions at a potential lower than that of the positive electrode,and an electrode in which a negative electrode mixture containing anegative electrode active material is held by a negative electrodecurrent collector, and an electrode formed of a negative electrodeactive material alone can be adopted.

(Negative Electrode Active Material)

As the negative electrode active material included in the negativeelectrode, materials that can be doped with or dedoped from lithium ionsat a potential lower than that of the positive electrode, such as carbonmaterials, chalcogen compounds (oxides, sulfides, and the like),nitrides, metals, and alloys can be adopted.

As the carbon materials that can be used as the negative electrodeactive material, graphite such as natural graphite and artificialgraphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and anorganic polymer compound calcined body can be adopted.

As the oxides that can be used as the negative electrode activematerial, oxides of silicon represented by the formula SiO_(x) (where, xis a positive real number) such as SiO₂ and SiO; oxides of titaniumrepresented by the formula TiO_(x) (where x is a positive real number)such as TiO₂ and TiO; oxides of vanadium represented by the formulaVO_(x) (where x is a positive real number) such as V₂O₅ and VO₂; oxidesof iron represented by the formula FeO_(x) (where x is a positive realnumber) such as Fe₃O₄, Fe₂O₃, and FeO; oxides of tin represented by theformula SnO_(x) (where x is a positive real number) such as SnO₂ andSnO; oxides of tungsten represented by a general formula WO_(x) (where,x is a positive real number) such as WO₃ and WO₂; and composite metaloxides containing lithium and titanium or vanadium such as Li₄Ti₅O₁₂ andLiVO₂ can be adopted.

As the sulfides that can be used as the negative electrode activematerial, sulfides of titanium represented by the formula TiS_(x)(where, x is a positive real number) such as Ti₂S₃, TiS₂, and TiS;sulfides of vanadium represented by the formula VS_(x) (where x is apositive real number) such V₃S₄, VS₂, and VS; sulfides of ironrepresented by the formula FeS_(x) (where x is a positive real number)such as Fe₃S₄, FeS₂, and FeS; sulfides of molybdenum represented by theformula MoS_(x) (where x is a positive real number) such as Mo₂S₃ andMoS₂; sulfides of tin represented by the formula SnS_(x) (where x is apositive real number) such as SnS₂ and SnS; sulfides of tungstenrepresented by WS_(x) (where x is a positive real number) such as WS₂;sulfides of antimony represented by the formula SbS_(x) (where x is apositive real number) such as Sb₂S₃; and sulfides of seleniumrepresented by the formula SeS_(x) (where x is a positive real number)such as Se₅S₃, SeS₂, and SeS can be adopted.

As the nitrides that can be used as the negative electrode activematerial, lithium-containing nitrides such as Li₃N and Li_(3-x)A_(x)N(where A is either one or both of Ni and Co, and 0<x<3 is satisfied) canbe adopted.

These carbon materials, oxides, sulfides, and nitrides may be usedsingly or in combination of two or more. In addition, these carbonmaterials, oxides, sulfides, and nitrides may be either crystalline oramorphous.

Moreover, as the metals that can be used as the negative electrodeactive material, lithium metal, silicon metal, tin metal, and the likecan be adopted.

As the alloys that can be used as the negative electrode activematerial, lithium alloys such as Li—Al, Li—Ni, Li—Si, Li—Sn, andLi—Sn—Ni; silicon alloys such as Si—Zn; tin alloys such as Sn—Mn, Sn—Co,Sn—Ni, Sn—Cu, and Sn—La; and alloys such as Cu₂Sb and La₃Ni₂Sn₇ can beadopted.

These metals and alloys are mainly used alone as an electrode afterbeing processed into, for example, a foil shape.

Among the above-mentioned negative electrode active materials, thecarbon material mainly including graphite such as natural graphite andartificial graphite is preferably used because the potential of thenegative electrode hardly changes from the uncharged state to the fullycharged state during charging (the potential flatness is good), theaverage discharge potential is low, and the capacity retention ratioduring repeated charging and discharging is high (the cyclecharacteristics are good). The shape of the carbon material may be, forexample, a flaky shape such as natural graphite, a spherical shape suchas mesocarbon microbeads, a fibrous shape such as graphitized carbonfiber, or an aggregate of fine powder.

The negative electrode mixture described above may contain a binder asnecessary. As the binder, a thermoplastic resin can be adopted, andspecifically, PVDF, thermoplastic polyimide, carboxymethylcellulose,polyethylene, and polypropylene can be adopted.

(Negative Electrode Current Collector)

As the negative electrode current collector included in the negativeelectrode, a long sheet-shaped member formed of a metal material, suchas Cu, Ni, and stainless steel, as the forming material can be adopted.Among these, it is preferable to use Cu as the forming material andprocess Cu into a thin film because Cu is less likely to form an alloywith lithium and can be easily processed.

As a method of causing the negative electrode current collector to holdthe negative electrode mixture, similarly to the case of the positiveelectrode, a method using press-forming, or a method of forming thenegative electrode mixture into a paste using a solvent or the like,applying the paste onto the negative electrode current collector, dryingthe paste, and pressing the paste to be compressed can be adopted.

(Separator)

As the separator included in the lithium secondary battery of thepresent embodiment, for example, a material having a form such as aporous film, non-woven fabric, or woven fabric made of a material suchas a polyolefin resin such as polyethylene and polypropylene, a fluorineresin, and a nitrogen-containing aromatic polymer can be used. Inaddition, two or more of these materials may be used to form theseparator, or these materials may be stacked to form the separator.

In the present embodiment, the air resistance of the separator accordingto the Gurley method defined by JIS P 8117 is preferably 50 sec/100 ccor more and 300 sec/100 cc or less, and more preferably 50 sec/100 cc ormore and 200 sec/100 cc or less in order for the electrolyte tofavorably permeate therethrough during battery use (during charging anddischarging).

In addition, the porosity of the separator is preferably 30 vol % ormore and 80 vol % or less, and more preferably 40 vol % or more and 70vol % or less. The separator may be a laminate of separators havingdifferent porosity.

(Electrolytic Solution)

The electrolytic solution included in the lithium secondary battery ofthe present embodiment contains an electrolyte and an organic solvent.

As the electrolyte contained in the electrolytic solution, lithiumcompounds such as LiClO₄, LiPF₆, LiAsF₆, LiSbF₆, LiBF₄, LiCF₃SO₃,LiN(SO₂CF₃)₂, LiN(SO₂C₂F₅)₂, LiN(SO₂CF₃)(COCF₃), Li(C₄F₉SO₃),LiC(SO₂CF₃)₃, Li₂B₁₀Cl₁₀, LiBOB (here, BOB refers tobis(oxalato)borate), LiFSI (here, FSI refers tobis(fluorosulfonyl)imide), lower aliphatic carboxylic acid lithiumcompounds, and LiAlCl₄ can be adopted, and a mixture of two or more ofthese may be used. Among these, as the electrolyte, it is preferable touse at least one selected from the group consisting of LiPF₆, LiAsF₆,LiSbF₆, LiBF₄, LiCF₃SO₃, LiN(SO₂CF₃)₂, and LiC(SO₂CF₃)₃, which containfluorine.

As the organic solvent included in the electrolytic solution, forexample, carbonates such as propylene carbonate, ethylene carbonate,dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate,4-trifluoromethyl-1,3-dioxolan-2-one, and1,2-di(methoxycarbonyloxy)ethane; ethers such as 1,2-dimethoxyethane,1,3-dimethoxypropane, pentafluoropropyl methyl ether,2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, and2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate,and g-butyrolactone; nitriles such as acetonitrile and butyronitrile;amides such as N,N-dimethylformamide and N,N-dimethylacetamide;carbamates such as 3-methyl-2-oxazolidone; and sulfur-containingcompounds such as sulfolane, dimethyl sulfoxide, and 1,3-propanesultone,or those obtained by introducing a fluoro group into these organicsolvents (those in which one or more of the hydrogen atoms of theorganic solvent are substituted with a fluorine atom) can be used.

As the organic solvent, it is preferable to use a mixture of two or morethereof. Among these, a mixed solvent containing a carbonate ispreferable, and a mixed solvent of a cyclic carbonate and a non-cycliccarbonate and a mixed solvent of a cyclic carbonate and an ether aremore preferable. As the mixed solvent of a cyclic carbonate and anon-cyclic carbonate, a mixed solvent containing ethylene carbonate,dimethyl carbonate, and ethyl methyl carbonate is preferable. Anelectrolytic solution using such a mixed solvent has many features suchas a wide operating temperature range, being less likely to deteriorateeven when charged and discharged at a high current rate, being lesslikely to deteriorate even during a long-term use, and beingnon-degradable even in a case where a graphite material such as naturalgraphite or artificial graphite is used as the negative electrode activematerial.

Furthermore, as the electrolytic solution, it is preferable to use anelectrolytic solution containing a lithium compound containing fluorinesuch as LiPF₆ and an organic solvent having a fluorine substituent inorder to enhance the safety of the obtained lithium secondary battery. Amixed solvent containing ethers having a fluorine substituent, such aspentafluoropropyl methyl ether and 2,2,3,3-tetrafluoropropyldifluoromethyl ether and dimethyl carbonate is even more preferablebecause the capacity retention ratio is high even when charging ordischarging is performed at a high current rate.

A solid electrolyte may be used instead of the electrolytic solution. Asthe solid electrolyte, for example, an organic polymer electrolyte suchas a polyethylene oxide-based polymer compound, or a polymer compoundcontaining at least one or more of a polyorganosiloxane chain or apolyoxyalkylene chain can be used. A so-called gel type in which anon-aqueous electrolyte is held in a polymer compound can also be used.Inorganic solid electrolytes containing sulfides such as Li₂S—SiS₂,Li₂S—GeS₂, Li₂S—P₂S₅, Li₂S—B₂S₃, Li₂S—SiS₂—Li₃PO₄, Li₂S—SiS₂—Li₂SO₄, andLi₂S—GeS₂—P₂S₅ can be adopted, and a mixture or two or more thereof maybe used. By using these solid electrolytes, the safety of the lithiumsecondary battery may be further enhanced.

In addition, in a case of using a solid electrolyte in the lithiumsecondary battery of the present embodiment, there may be cases wherethe solid electrolyte plays a role of the separator, and in such a case,the separator may not be required.

Since the positive electrode active material having the above-describedconfiguration uses the lithium-containing transition metal compositeoxide of the present embodiment described above, in the lithiumsecondary battery using the positive electrode active material, sidereactions that occur inside the battery can be suppressed.

Moreover, since the positive electrode having the above-describedconfiguration has the positive electrode active material for a lithiumsecondary battery of the present embodiment described above, in thelithium secondary battery, side reactions that occur inside the batterycan be suppressed.

Furthermore, since the lithium secondary battery having theabove-described configuration has the positive electrode describedabove, a lithium secondary battery in which side reactions occurringinside the battery is suppressed compared to the related art can beachieved.

Another aspect of the present invention is as follows.

[1] A lithium-containing transition metal composite oxide including:secondary particles that are aggregates of primary particles into orfrom which lithium ions are dopable or dedopable, in which thelithium-containing transition metal composite oxide satisfies thefollowing conditions,

(1) the lithium-containing transition metal composite oxide isrepresented by Formula (I),

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0<x≤0.2, 0.05<y≤0.25, 0≤z≤0.4, 0≤w≤0.5, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn),

(2) when an area value of a peak appearing at 53.8 eV in a lithium isspectrum is referred to as a and an area value of a peak appearing at529.0 eV in an oxygen s spectrum is referred to as β when X-rayphotoelectron spectroscopy is performed, and a ratio between α and β isreferred to as γ (α/β=γ),

γ is calculated for each of a surface of the secondary particle and aninside of the secondary particle, and when a γ value of the surface ofthe secondary particle is referred to as γ1 and a γ value of the insideof the secondary particle is referred to as γ2, γ1 and γ2 satisfy acondition of Formula (II).

0.3≤γ1/γ2≤1.0  (II)

[2] In the lithium-containing transition metal composite oxide accordingto [1], in which an element ratio R (Li (Atom %)/O (Atom %)) calculatedfrom the peak appearing at 53.8 eV in the lithium 1s spectrum and thepeak appearing at 529.0 eV in the oxygen 1s spectrum when the X-rayphotoelectron spectroscopy is performed is 0.45≤R≤0.75 in the inside ofthe secondary particle.

[3] The BET specific surface area (m²/g) of the lithium-containingtransition metal composite oxide according to [1] or [2] is 0.15 or moreand 2.5 or less.

[4] The BET specific surface area (m²/g) of the lithium-containingtransition metal composite oxide according to [1] or [2] is 0.15 or moreand 1.5 or less.

[5] In a powder X-ray diffraction measurement of the lithium-containingtransition metal composite oxide according to any one of [1] to [4]using CuKα radiation, a crystallite size L₀₀₃ at a peak within a rangeof 20=18.7±1° is 700 Å or more and 1200 Å or less.

[6] The 50% cumulative volume particle size D₅₀ (μm) of thelithium-containing transition metal composite oxide according to any oneof [1] to [5] is 3 or more and 15 or less, and a difference between amaximum particle diameter D_(max) and a minimum particle size D_(min)(μm) is D₅₀×2/3 or more.

[7] The 50% cumulative volume particle size D₅₀ (μm) of thelithium-containing transition metal composite oxide according to any oneof [1] to [5] is 10 or more and 15 or less, and the difference betweenthe maximum particle diameter D_(max) and the minimum particle sizeD_(min) (μm) may be D₅₀×2/3 or more.

[8] A positive electrode for a lithium secondary battery in which a massratio between a positive electrode active material for a lithiumsecondary battery including the lithium-containing transition metalcomposite oxide according to any one of [1] to [7], acetylene black, andPVDF is the positive electrode active material for a lithium secondarybattery:acetylene black:PVDF=92:5:3 and an electrode area is 1.65 cm² isformed, a coin type battery R2032 is produced including the positiveelectrode for a secondary battery, a separator in which a heat-resistantporous layer is laminated on a polyethylene porous film, an electrolyticsolution obtained by dissolving LiPF₆ in a mixed solution of ethylenecarbonate, dimethyl carbonate, and ethyl methyl carbonate in a ratio of30:35:35 (volume ratio) to achieve 1.0 mol/l, and a metal lithiumnegative electrode for a secondary battery, and when a discharge ratetest was performed as follows on the coin type battery R2032 under thefollowing charge/discharge test conditions, the obtained discharge ratecharacteristics were 27% to 98%.

[Discharge Rate Characteristics]

The discharge rate characteristics (%) as an index of rate performancewere calculated by measuring and calculating a 1.0 C discharge capacityand a 5.0 C discharge capacity and dividing the 5.0 C discharge capacityobtained by the measurement by the 1.0 C capacity also obtained by themeasurement.

[9] A method for manufacturing a lithium-containing transition metalcomposite oxide including secondary particles that are aggregates ofprimary particles into or from which lithium ions are dopable ordedopable and represented by General Formula (I), the method including:a mixing step of mixing a lithium compound and a metal compositecompound containing at least nickel to obtain a mixture; a calciningstep of calcining the mixture to obtain a calcined product; and awashing step of washing the calcined product, in which, in the mixingstep, mixing is performed so that a molar ratio (Li/Me, a molar ratio oflithium to a total amount of metal elements excluding lithium) betweenlithium contained in the lithium compound and metal elements in themetal composite compound containing at least nickel exceeds 1, and

in the washing step, a temperature of a washing solution used forwashing is set to 0° C. or higher and 10° C. or lower, washing isperformed in an amount of the washing solution used for washing suchthat a concentration of lithium carbonate in the washing solution in acase where it is assumed that a total amount of residual lithiumcarbonate contained in the calcined product before washing is dissolvedin the washing solution is 1/10 or more and 3 or less times a solubilityof lithium carbonate in the washing solution at the temperature of thewashing solution during the washing step, and a temperature of a slurrycontaining the calcined product and the washing solution used forwashing is maintained at −20° C. or higher and lower than 10° C.

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0≤x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn)

[10] A method for manufacturing a lithium-containing transition metalcomposite oxide including secondary particles that are aggregates ofprimary particles into or from which lithium ions are dopable ordedopable and represented by General Formula (I), the method including:a mixing step of mixing a lithium compound and a metal compositecompound containing at least nickel to obtain a mixture; a calciningstep of calcining the mixture to obtain a calcined product; a washingstep of washing the calcined product; and a re-calcining step ofre-calcining the washed calcined product,

in which, in the mixing step, mixing is performed so that a molar ratio(Li/Me, a molar ratio of lithium to a total amount of metal elementsexcluding lithium) between lithium contained in the lithium compound andmetal elements in the metal composite compound containing at leastnickel exceeds 1, and

in the washing step, a temperature of a washing solution used forwashing is set to −20° C. or higher and 40° C. or lower, and washing isperformed in an amount of the washing solution used for washing suchthat a concentration of lithium carbonate in the washing solution in acase where it is assumed that a total amount of residual lithiumcarbonate contained in the calcined product before washing is dissolvedin the washing solution is ⅕ or more and 3 or less times a solubility oflithium carbonate in the washing solution at the temperature of thewashing solution in the washing step.

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0≤x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

Another aspect of the present invention is as follows.

[1] A lithium-containing transition metal composite oxide including:secondary particles that are aggregates of primary particles into orfrom which lithium ions are dopable or dedopable, in which thelithium-containing transition metal composite oxide satisfies thefollowing conditions,

(1) the lithium-containing transition metal composite oxide isrepresented by Formula (I),

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0<x<0.2, 0<y<0.5, 0<z<0.8, 0<w<0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn),

(2) when an area value of a peak appearing at 53.8 eV in a lithium isspectrum is referred to as a and an area value of a peak appearing at529.0 eV in an oxygen 1s spectrum is referred to as β when X-rayphotoelectron spectroscopy is performed, and a ratio between α and ρ isreferred to as γ (α/β=γ),

γ is calculated for each of a surface of the secondary particle and aninside of the secondary particle, and when a γ value of the surface ofthe secondary particle is referred to as γ1 and a γ value of the insideof the secondary particle is referred to as γ2, γ1 and γ2 satisfy acondition of Formula (II).

0.3≤γ1/γ2≤0.95  (II)

[2] The lithium-containing transition metal composite oxide according to[1], in which an element ratio R (Li (Atom %)/O (Atom %)) calculatedfrom the peak appearing at 53.8 eV in the lithium 1s spectrum and thepeak appearing at 529.0 eV in the oxygen 1s spectrum when the X-rayphotoelectron spectroscopy is performed is 0.4<R<0.8 in the inside ofthe secondary particle.

[3] The lithium-containing transition metal composite oxide according to[1] or [2], in which a BET specific surface area (m²/g) is 0.1 or moreand 3.0 or less.

[4] The lithium-containing transition metal composite oxide according toany one of [1] to [3], in which a crystallite size L₀₀₃ at a peak withina range of 2θ=18.7±1° in a powder X-ray diffraction measurement usingCuKα radiation is 400 Å or more and 1300 Å or less.

[5] The lithium-containing transition metal composite oxide according toany one of [1] to [4], in which a 50% cumulative volume particle sizeD₅₀ (μm) is 3 or more and 20 or less, and a difference between a maximumparticle diameter D_(max) and a minimum particle size D_(min) (μm) isD₅₀×2/3 or more.

[6] A positive electrode active material for a lithium secondarybattery, including: the lithium-containing transition metal compositeoxide according to any one of [1] to [5].

[7] A positive electrode for a lithium secondary battery, including: thepositive electrode active material for a lithium secondary batteryaccording to [6].

[8] A lithium secondary battery including: the positive electrode for alithium secondary battery according to [7].

[9] A method for manufacturing a lithium-containing transition metalcomposite oxide including secondary particles that are aggregates ofprimary particles into or from which lithium ions are dopable ordedopable and represented by General Formula (I), the method including:a mixing step of mixing a lithium compound and a metal compositecompound containing at least nickel to obtain a mixture; a calciningstep of calcining the mixture to obtain a calcined product; and awashing step of washing the calcined product,

in which, in the mixing step, mixing is performed so that a molar ratio(Li/Me, a molar ratio of lithium to a total amount of metal elementsexcluding lithium) between lithium contained in the lithium compound andmetal elements in the metal composite compound containing at leastnickel exceeds 1, and

in the washing step, a temperature of a washing solution used forwashing is set to −20° C. or higher and 40° C. or lower, and washing isperformed in an amount of the washing solution used for washing suchthat a concentration of lithium carbonate in a case where it is assumedthat a total amount of residual lithium carbonate contained in thecalcined product before washing is dissolved in the washing solution is1/10 or more and 3 or less times a solubility of lithium carbonate inthe washing solution at the temperature of the washing solution duringthe washing step.

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0<x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

[10] A method for manufacturing a lithium-containing transition metalcomposite oxide including secondary particles that are aggregates ofprimary particles into or from which lithium ions are dopable ordedopable and represented by General Formula (I), the method including:a mixing step of mixing a lithium compound and a metal compositecompound containing at least nickel to obtain a mixture; a calciningstep of calcining the mixture to obtain a calcined product; and awashing step of washing the calcined product,

in which, in the mixing step, mixing is performed so that a molar ratio(Li/Me, a molar ratio of lithium to a total amount of metal elementsexcluding lithium) between lithium contained in the lithium compound andmetal elements in the metal composite compound containing at leastnickel exceeds 1, and

in the washing step, a temperature of a slurry containing the calcinedproduct and a washing solution used for washing is maintained at −20° C.or higher and lower than 10° C. or lower, and washing is performed in anamount of the washing solution used for washing such that aconcentration of lithium carbonate in the washing solution in a casewhere it is assumed that a total amount of residual lithium carbonatecontained in the calcined product before washing is dissolved in thewashing solution is 1/10 or more and 3 or less times a saturatedsolubility of lithium carbonate at the temperature of the washingsolution during the washing step.

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0<x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

[11] A method for manufacturing a lithium-containing transition metalcomposite oxide including secondary particles that are aggregates ofprimary particles into or from which lithium ions are dopable ordedopable and represented by General Formula (I), the method including:a mixing step of mixing a lithium compound and a metal compositecompound containing at least nickel to obtain a mixture; a calciningstep of calcining the mixture to obtain a calcined product; and awashing step of washing the calcined product,

in which, in the mixing step, mixing is performed so that a molar ratio(Li/Me) between lithium contained in the lithium compound and metalelements in the metal composite compound containing at least nickelexceeds 1, and

in the washing step, a temperature of a washing solution used forwashing is set to −20° C. or higher and 40° C. or lower, washing isperformed in an amount of the washing solution used for washing suchthat a concentration of lithium carbonate in the washing solution in acase where it is assumed that a total amount of residual lithiumcarbonate contained in the calcined product before washing is dissolvedin the washing solution is 1/10 or more and 3 or less times a solubilityof lithium carbonate in the washing solution at the temperature of thewashing solution during the washing step, and a temperature of a slurrycontaining the calcined product and the washing solution used forwashing is maintained at −20° C. or higher and lower than 10° C.

Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I)

(in Formula (I), 0<x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 aresatisfied, and M represents one or more metals selected from the groupconsisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V,W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

EXAMPLES

Next, the present invention will be described in more detail withreference to examples.

In this example, the evaluation of a lithium-containing transition metalcomposite oxide and a positive electrode active material for a lithiumsecondary battery, and the preparation and evaluation of a positiveelectrode and a lithium secondary battery were performed as follows.

<Compositional Analysis of Positive Electrode Active Material forLithium Secondary Battery>

The compositional analysis of a positive electrode active material for alithium secondary battery manufactured by the method described below wasperformed by using an inductively coupled plasma emission analyzer (SPS3000, manufactured by SII Nano Technology Inc.) after dissolving thepowder of the obtained positive electrode active material for a lithiumsecondary battery in hydrochloric acid.

<<X-ray Photoelectron Spectroscopy (XPS)>>

Measurement of γ1/γ2

A lithium-containing transition metal composite oxide manufactured bythe method described below was analyzed by XPS (Quantera SXM,manufactured by ULVAC-PHI, Inc.).

Specifically, first, the obtained lithium-containing transition metalcomposite oxide was provided in a dedicated substrate. Next, using AlKαradiation, measurement was performed by charge neutralization byelectrons and Ar ions with a photoelectron extraction angle of 45degrees and an aperture diameter of 100 μm, whereby data was obtained.

Then, using the XPS data analysis software MuitiPak, charge correctionwas performed with the peak attributed to surface contaminationhydrocarbons in a carbon Is spectrum at 284.6 eV, and waveformseparation by peak fitting was performed on a peak in a lithium 1sspectrum and a peak in an oxygen 1s spectrum.

A peak area value a appearing at 53.8 eV in the lithium 1s spectrum anda peak area value β appearing at 529.0 eV in the oxygen 1s spectrum werecalculated.

Thereafter, the ratio γ (α/β) between α and β was calculated. Here, γwas calculated for the surface of secondary particles and the inside ofthe secondary particles, and the γ value of the surface of the secondaryparticles was referred to as γ1 while the γ value of the inside of thesecondary particles was referred to as γ2.

In order to calculate γ1, for the XPS measurement of the surface of thesecondary particles, using the lithium-containing transition metalcomposite oxide manufactured by the method described below was providedas it is.

In order to calculate γ2, for the XPS measurement of the inside of thesecondary particles, Ar ions sputtering was performed on the secondaryparticles in an XPS apparatus under the same conditions as in the caseof a SiO₂ film, which was sputtered to a depth of 10 nm. Thereafter, XPSmeasurement was performed on the exposed region.

At the same point, Ar ion sputtering was performed again under the sameconditions as in the case of the SiO₂ film sputtered to a depth of 10nm. Thereafter, XPS measurement was performed again at the same point.This operation was repeated, and the value when no change appeared inthe γ value was used as γ2.

Measurement of Element Ratio R (Li (Atom %)/O (Atom %))

The lithium-containing transition metal composite oxide manufactured bythe method described below was analyzed by XPS under the same conditionsas described above. In the region where γ2 was calculated, the elementratio R (Li (Atom %)/O (Atom %)) was calculated from the area value ofthe peak appearing at 53.8 eV in the lithium 1s spectrum and the areavalue of the peak appearing at 529.0 eV in the oxygen 1s spectrum.

<<Measurement of BET Specific Surface Area of Lithium-ContainingTransition Metal Composite Oxide>>

After 1 g of the powder of the lithium-containing transition metalcomposite oxide to be measured was dried in a nitrogen atmosphere at150° C. for 15 minutes, the powder was measured using Flowsorb II 2300manufactured by Micromeritics Instrument Corp.

<<Measurement of Crystallite Size of Lithium-Containing Transition MetalComposite Oxide>>

Powder X-ray diffraction measurement of the lithium-containingtransition metal composite oxide was performed using an X-raydiffractometer (X'Prt PRO manufactured by Malvern Panalytical Ltd). Theobtained lithium-containing transition metal composite oxide wasprovided in a dedicated substrate, and measurement was performed using aCuKα radiation source at a diffraction angle in a range of 20=10° to 90°to obtain a powder X-ray diffraction pattern. Using powder X-raydiffraction pattern comprehensive analysis software JADE 5, thehalf-width of a peak corresponding to the peak A was obtained from thepowder X-ray diffraction pattern, and the crystallite size L₀₀₃ wascalculated by the Scherrer equation.

<<Measurement of 50% Cumulative Volume Particle Size D₅₀ ofLithium-Containing Transition Metal Composite Oxide>>

0.1 g of the powder of the lithium-containing transition metal compositeoxide to be measured was poured into 50 ml of 0.2 mass % sodiumhexametaphosphate aqueous solution to obtain a dispersion solution inwhich the powder was dispersed. The particle size distribution of theobtained dispersion solution was measured using Mastersizer 2000manufactured by Malvern Instruments Ltd. (laser diffraction scatteringparticle size distribution measuring device) to obtain a volume-basedcumulative particle size distribution curve. In the obtained cumulativeparticle size distribution curve, the volume particle size at a 50%cumulative point was referred to as a 50% cumulative volume particlesize D₅₀ of the positive electrode active material for a lithiumsecondary battery. Furthermore, in the obtained cumulative particle sizedistribution curve, the maximum volume particle size was referred to asD_(max), and the minimum volume particle size was referred to asD_(min).

[Production of Lithium Secondary Battery]

Production of Positive Electrode for Lithium Secondary Battery

A paste-like positive electrode mixture was prepared by adding thelithium-containing transition metal composite oxide obtained by themanufacturing method described below, a conductive material (acetyleneblack), and a binder (PVDF) to achieve a composition of positiveelectrode active material for a lithium secondary battery:conductivematerial:binder=92:5:3 (mass ratio) and performing kneading thereon.During the preparation of the positive electrode mixture,N-methyl-2-pyrrolidone was used as an organic solvent.

The obtained positive electrode mixture was applied to a 40 μm-thick Alfoil serving as a current collector and dried at 150° C. for 8 hours toobtain a positive electrode for a lithium secondary battery. Theelectrode area of the positive electrode for a lithium secondary batterywas set to 1.65 cm².

Production of Lithium Secondary Battery (Coin Type Cell)

The following operation was performed in a glove box in a dry airatmosphere.

The positive electrode for a lithium secondary battery produced in“Production of Positive Electrode for Lithium Secondary Battery” wasplaced on the lower lid of a coin cell for coin type battery R2032(manufactured by Hohsen Corp.) with the aluminum foil surface facingdownward, and a laminated film separator (a heat-resistant porous layer(thickness 16 mm) was laminated on a polyethylene porous film) wasplaced thereon. 300 μL of an electrolytic solution was injectedthereinto. The electrolytic solution used was prepared by dissolving, ina mixed solution of ethylene carbonate, dimethyl carbonate, and ethylmethyl carbonate in a ratio of 30:35:35 (volume ratio), LiPF₆ to achieve1.0 mol/L.

Next, metal lithium was used as a negative electrode, and the negativeelectrode was placed on the upper side of the laminated film separator,covered with the upper lid via a gasket, and caulked by a caulkingmachine, whereby a lithium secondary battery (coin type battery R2032,hereinafter, sometimes referred to as “coin type battery”) was produced.

[Discharge Rate Characteristics]

The discharge rate characteristics were calculated by measuring each ofa 1.0 C discharge capacity and a 5.0 C discharge capacity. By dividingthe 5.0 C discharge capacity obtained by the measurement by the 1.0 Ccapacity also obtained by the measurement, the discharge ratecharacteristics as an index of rate performance were calculated. InTable 1, “DCG. 1C” means the discharge capacity (unit: mAh/g) at 1.0 C.

In addition, “DCG. 5C” means the discharge capacity (unit: mAh/g) at 5.0C.

Example 1 1. Manufacturing of Lithium-Containing Transition MetalComposite Oxide 1

After water was put in a reaction tank equipped with a stirrer and anoverflow pipe, an aqueous solution of sodium hydroxide was addedthereto, and the liquid was maintained at a temperature of 60° C.

An aqueous solution of nickel sulfate, an aqueous solution of cobaltsulfate, an aqueous solution of manganese sulfate, and an aqueoussolution of aluminum sulfate were mixed so that the atomic ratio betweennickel atoms, cobalt atoms, manganese atoms, and aluminum atoms became87.5:9.5:2:1, whereby a mixed raw material solution was prepared.

Next, the mixed raw material solution and an aqueous solution ofammonium sulfate as a complexing agent were continuously added into thereaction tank under stirring, and an oxygen-containing gas was flowedwhile stirring the solution in the reaction tank at 750 rpm using astirring blade. An aqueous solution of sodium hydroxide wasappropriately added dropwise so that the pH of the solution in thereaction tank when measured at 40° C. became 12.3 to obtain nickelcobalt manganese aluminum composite hydroxide particles, and theparticles were washed with a sodium hydroxide solution, thereafterdehydrated by a centrifuge, isolated, and dried at 105° C., whereby anickel cobalt manganese aluminum composite hydroxide 1 was obtained.

The nickel cobalt manganese aluminum composite hydroxide 1 obtained asdescribed above was calcined at 650° C. for 5 hours in a dry airatmosphere to obtain a nickel cobalt manganese aluminum composite oxide1.

The obtained nickel cobalt manganese aluminum composite oxide 1 andlithium hydroxide powder were weighed to achieve Li/(Ni+Co+Mn+Al)=1.10in terms of molar ratio and mixed. Thereafter, the mixture was calcinedin an oxygen atmosphere at 760° C. for 5 hours to obtain a calcinedproduct 1.

Next, the amount of lithium carbonate remaining in the calcined product1 was measured by neutralization titration. Then, a slurry-like liquidwas prepared by adding 1000 g of the calcined product 1 to 1500 g ofpure water at 25° C., the slurry-like liquid was stirred for 10 minuteswhile being maintained at 25° C., and the obtained slurry-like liquidwas subjected to centrifugal filtration to obtain a wet cake.Thereafter, the wet cake was dried in an air atmosphere at 150° C. for12 hours to obtain a dried powder 1.

900 g of the dried powder 1 was collected, and 7.1 g of aluminananopowder was applied thereto and calcined in an oxygen atmosphere at760° C. for 10 hours to obtain a target lithium-containing transitionmetal composite oxide 1.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide 1

Compositional analysis of the obtained positive electrode activematerial 1 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.00,y=0.095, z=0.02, and w=0.01 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material 1 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material 1 for alithium secondary battery are described in Table 1.

In addition, the temperature (° C.) of the washing solution used forwashing, the temperature (° C.) of the slurry, the amount of residuallithium carbonate (g) contained in 1000 g of the calcined product 1, andthe saturated dissolution amount (g) when lithium carbonate wasdissolved in 100 g of the washing solution are described in Table 2.

Example 2 1. Manufacturing of Lithium-Containing Transition MetalComposite Oxide 2

900 g of the dried powder 1 obtained in Example 1 was collected andcalcined in an oxygen atmosphere at 760° C. for 10 hours to obtain atarget lithium-containing transition metal composite oxide 2.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide 2

Compositional analysis of the obtained positive electrode activematerial 2 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.01,y=0.095, z=0.02, and w=0.01 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material 2 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material 2 for alithium secondary battery are described in Table 1.

Example 3 1. Manufacturing of Lithium-Containing Transition MetalComposite Oxide 3

The nickel cobalt manganese aluminum composite oxide 1 obtained inExample 1 and lithium hydroxide powder were weighed to achieveLi/(Ni+Co+Mn+Al)=1.15 in terms of molar ratio and mixed. Thereafter, themixture was calcined in an oxygen atmosphere at 720° C. for 10 hours toobtain a calcined product 3.

Next, the amount of lithium carbonate remaining in the calcined product3 was measured by neutralization titration. Then, a slurry-like liquidwas prepared by adding 1000 g of the calcined product 3 to 1325 g ofpure water at 25° C., the slurry-like liquid was stirred for 10 minuteswhile being maintained at 25° C., and the obtained slurry-like liquidwas subjected to centrifugal filtration to obtain a wet cake.Thereafter, the wet cake was dried in an air atmosphere at 150° C. for12 hours to obtain a dried powder 3.

The dried powder 3 was calcined in an oxygen atmosphere at 760° C. for10 hours to obtain a target lithium-containing transition metalcomposite oxide 3.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide 3

Compositional analysis of the obtained positive electrode activematerial 3 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.02,y=0.095, z=0.02, and w=0.01 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material 3 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material 3 for alithium secondary battery are described in Table 1.

In addition, the temperature (° C.) of the washing solution used forwashing, the temperature (° C.) of the slurry, the amount of residuallithium carbonate (g) contained in 1000 g of the calcined product 3, andthe saturated dissolution amount (g) when lithium carbonate wasdissolved in 100 g of the washing solution are described in Table 2.

Example 4

Manufacturing of Lithium-Containing Transition Metal Composite Oxide 4The nickel cobalt manganese aluminum composite oxide 1, lithiumhydroxide powder, and tungsten oxide powder were weighed to achieveLi/(Ni+Co+Mn+Al)=1.10 and W/(Ni+Co+Mn+Al)=0.004 in terms of molar ratioand mixed.

Thereafter, the mixture was calcined in an oxygen atmosphere at 760° C.for 5 hours to obtain a calcined product 4.

Next, the amount of lithium carbonate remaining in the calcined product4 was measured by neutralization titration. Then, a slurry-like liquidwas prepared by adding 1000 g of the calcined product 4 to 1083 g ofpure water at 25° C., the slurry-like liquid was stirred for 10 minuteswhile being maintained at 25° C., and the obtained slurry-like liquidwas subjected to centrifugal filtration to obtain a wet cake.Thereafter, the wet cake was dried in an air atmosphere at 150° C. for12 hours to obtain a dried powder 4.

900 g of the dried powder 4 was collected, and 7.1 g of aluminananopowder was applied thereto and calcined in an oxygen atmosphere at760° C. for 10 hours to obtain a target lithium-containing transitionmetal composite oxide 4.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide 4

Compositional analysis of the obtained positive electrode activematerial 4 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.01,y=0.095, z=0.02, and w=0.01 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min)(μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material 4 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material 4 for alithium secondary battery are described in Table 1.

In addition, the temperature (° C.) of the washing solution used forwashing, the temperature (° C.) of the slurry, the amount of residuallithium carbonate (g) contained in 1000 g of the calcined product 4, andthe saturated dissolution amount (g) when lithium carbonate wasdissolved in 100 g of the washing solution are described in Table 2.

Example 5 1. Manufacturing of Lithium-Containing Transition MetalComposite Oxide 5

1000 g of the calcined product 4 was collected, a slurry-like liquid wasprepared by adding 1000 g of pure water at 25° C., the slurry-likeliquid was stirred for 10 minutes while being maintained at 25° C., andthe obtained slurry-like liquid was subjected to centrifugal filtrationto obtain a wet cake. Thereafter, the wet cake was dried in an airatmosphere at 150° C. for 12 hours to obtain a dried powder 5.

900 g of the dried powder 5 was collected, and 7.1 g of aluminananopowder was applied thereto and calcined in an oxygen atmosphere at760° C. for 10 hours to obtain a target lithium-containing transitionmetal composite oxide 5.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide 5

Compositional analysis of the obtained positive electrode activematerial 5 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.00,y=0.095, z=0.02, and w=0.01 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material 5 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material 5 for alithium secondary battery are described in Table 1.

In addition, the temperature (° C.) of the washing solution used forwashing, the temperature (° C.) of the slurry, the amount of residuallithium carbonate (g) contained in 1000 g of the calcined product 4, andthe saturated dissolution amount (g) when lithium carbonate wasdissolved in 100 g of the washing solution are described in Table 2.

Example 6 1. Manufacturing of Lithium-Containing Transition MetalComposite Oxide 6

1000 g of the calcined product 4 was collected, a slurry-like liquid wasprepared by adding 3000 g of pure water at 25° C., the slurry-likeliquid was stirred for 10 minutes while being maintained at 25° C., andthe obtained slurry-like liquid was subjected to centrifugal filtrationto obtain a wet cake. Thereafter, the wet cake was dried in an airatmosphere at 150° C. for 12 hours to obtain a dried powder 6.

900 g of the dried powder 6 was collected, and 7.1 g of aluminananopowder was applied thereto and calcined in an oxygen atmosphere at760° C. for 10 hours to obtain a target lithium-containing transitionmetal composite oxide 6.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide 6

Compositional analysis of the obtained positive electrode activematerial 6 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.00,y=0.095, z=0.02, and w=0.01 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material 6 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material 6 for alithium secondary battery are described in Table 1.

In addition, the temperature (° C.) of the washing solution used forwashing, the temperature (° C.) of the slurry, the amount of residuallithium carbonate (g) contained in 1000 g of the calcined product 6, andthe saturated dissolution amount (g) when lithium carbonate wasdissolved in 100 g of the washing solution are described in Table 2.

Example 7 1. Manufacturing of Lithium-Containing Transition MetalComposite Oxide 7

After water was put in a reaction tank equipped with a stirrer and anoverflow pipe, an aqueous solution of sodium hydroxide was addedthereto, and the liquid was maintained at a temperature of 50° C.

An aqueous solution of nickel sulfate, an aqueous solution of cobaltsulfate, an aqueous solution of aluminum sulfate were mixed so that theatomic ratio between nickel atoms, cobalt atoms, and aluminum atomsbecame 88:9:3, whereby a mixed raw material solution was prepared.

Next, the mixed raw material solution and an aqueous solution ofammonium sulfate as a complexing agent were continuously added into thereaction tank under stirring, and an oxygen-containing gas was flowedwhile stirring the solution in the reaction tank at 750 rpm using astirring blade. An aqueous solution of sodium hydroxide wasappropriately added dropwise so that the pH of the solution in thereaction tank when measured at 40° C. became 11.2 to obtain nickelcobalt aluminum composite hydroxide particles, and the particles werewashed with a sodium hydroxide solution, thereafter dehydrated by acentrifuge, isolated, and dried at 105° C., whereby a nickel cobaltaluminum composite hydroxide 7 was obtained.

The nickel cobalt aluminum composite hydroxide 7 obtained as describedabove was calcined in an air atmosphere at 600° C. for 8 hours to obtaina nickel cobalt aluminum composite oxide 7.

The obtained nickel cobalt aluminum composite oxide 7 and lithiumhydroxide powder were weighed to achieve Li/(Ni+Co+Al)=1.10 in terms ofmolar ratio and mixed. Thereafter, the mixture was calcined in an oxygenatmosphere at 720° C. for 6 hours to obtain a calcined product 7.

Next, the amount of lithium carbonate remaining in the calcined product7 was measured by neutralization titration. Then, a slurry-like liquidwas prepared by adding 1000 g of the calcined product 7 to 2846 g ofpure water at 5° C., the slurry-like liquid was stirred for 20 minuteswhile being maintained at 5° C., and the obtained slurry-like liquid wassubjected to centrifugal filtration to obtain a wet cake. Thereafter,the wet cake was dried at 150° C. for 8 hours to obtain a targetlithium-containing transition metal composite oxide 7.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide 7

Compositional analysis of the obtained positive electrode activematerial 7 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.01,y=0.09, z=0.00, and w=0.03 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material 7 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material 7 for alithium secondary battery are described in Table 1.

In addition, the temperature (° C.) of the washing solution used forwashing, the temperature (° C.) of the slurry, the amount of residuallithium carbonate (g) contained in 1000 g of the calcined product 7, andthe saturated dissolution amount (g) when lithium carbonate wasdissolved in 100 g of the washing solution are described in Table 2.

Example 8 1. Manufacturing of Lithium-Containing Transition MetalComposite Oxide

After water was put in a reaction tank equipped with a stirrer and anoverflow pipe, an aqueous solution of sodium hydroxide was addedthereto, and the liquid was maintained at a temperature of 50° C.

An aqueous solution of nickel sulfate, an aqueous solution of cobaltsulfate, and an aqueous solution of manganese sulfate were mixed so thatthe atomic ratio between nickel atoms, cobalt atoms, manganese atoms,and manganese atoms became 55:21:24, whereby a mixed raw materialsolution was prepared.

Next, the mixed raw material solution and an aqueous solution ofammonium sulfate as a complexing agent were continuously added into thereaction tank under stirring, and an oxygen-containing gas was flowedwhile stirring the solution in the reaction tank at 750 rpm using astirring blade. An aqueous solution of sodium hydroxide wasappropriately added dropwise so that the pH of the solution in thereaction tank when measured at 40° C. became 11.4 to obtain nickelcobalt manganese composite hydroxide particles, and the particles werewashed with a sodium hydroxide solution, thereafter dehydrated by acentrifuge, isolated, and dried at 105° C., whereby a nickel cobaltmanganese composite hydroxide 8 was obtained.

The nickel cobalt manganese composite hydroxide 8 obtained as describedabove was calcined at 850° C. for 8 hours in an air atmosphere to obtaina nickel cobalt manganese composite oxide 8.

The obtained nickel cobalt manganese composite oxide 8 and lithiumhydroxide powder were weighed to achieve Li/(Ni+Co+Mn)=1.07 in terms ofmolar ratio and mixed. Thereafter, the mixture was calcined in an oxygenatmosphere at 850° C. for 6 hours to obtain a target lithium-containingtransition metal composite oxide 8.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide 8

Compositional analysis of the obtained positive electrode activematerial 8 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.04,y=0.21, z=0.24, and w=0.00 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material 8 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material 8 for alithium secondary battery are described in Table 1.

Example 9 1. Manufacturing of Lithium-Containing Transition MetalComposite Oxide 9

The amount of lithium carbonate remaining in the calcined product 7obtained in Example 7 was measured by neutralization titration. Then, aslurry-like liquid was prepared by adding 100 g of the calcined product7 to 284.6 g of pure water at 8° C., the slurry-like liquid was stirredfor 20 minutes while being maintained at 8° C., and the obtainedslurry-like liquid was subjected to centrifugal filtration to obtain awet cake. Thereafter, the wet cake was dried at 150° C. for 8 hours toobtain a target lithium-containing transition metal composite oxide 9.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide 9

Compositional analysis of the obtained positive electrode activematerial 9 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.02,y=0.09, z=0.00, and w=0.03 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material 9 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material 9 for alithium secondary battery are described in Table 1.

In addition, the temperature (° C.) of the washing solution used forwashing, the temperature (° C.) of the slurry, the amount of residuallithium carbonate (g) contained in 1000 g of the calcined product 7, andthe saturated dissolution amount (g) when lithium carbonate wasdissolved in 100 g of the washing solution are described in Table 2.

Comparative Example 1 1. Manufacturing of Lithium-Containing TransitionMetal Composite Oxide C1

The nickel cobalt manganese aluminum composite oxide 1 and lithiumhydroxide powder were weighed to achieve Li/(Ni+Co+Mn+Al)=1.02 in termsof molar ratio and mixed. Thereafter, the mixture was calcined in anoxygen atmosphere at 760° C. for 5 hours to obtain a calcined productC1.

Next, the amount of lithium carbonate remaining in the calcined productC1 was measured by neutralization titration. Thereafter, the calcinedproduct C1 was calcined in an oxygen atmosphere at 760° C. for 10 hoursto obtain a target lithium-containing transition metal composite oxideC1.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide C1

Compositional analysis of the obtained positive electrode activematerial C1 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=−0.00,y=0.095, z=0.02, and w=0.01 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material C1 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material C1 for alithium secondary battery are described in Table 1.

Comparative Example 2 1. Manufacturing of Lithium-Containing TransitionMetal Composite Oxide C2

After water was put in a reaction tank equipped with a stirrer and anoverflow pipe, an aqueous solution of sodium hydroxide was addedthereto, and the liquid was maintained at a temperature of 50° C.

An aqueous solution of nickel sulfate, an aqueous solution of cobaltsulfate, an aqueous solution of aluminum sulfate were mixed so that theatomic ratio between nickel atoms, cobalt atoms, and aluminum atomsbecame 82:15:3, whereby a mixed raw material solution was prepared.

Next, the mixed raw material solution and an aqueous solution ofammonium sulfate as a complexing agent were continuously added into thereaction tank under stirring, and an oxygen-containing gas was flowedwhile stirring the solution in the reaction tank at 350 rpm using astirring blade. An aqueous solution of sodium hydroxide wasappropriately added dropwise so that the pH of the solution in thereaction tank when measured at 40° C. became 11.5 to obtain nickelcobalt aluminum composite hydroxide particles, and the particles werewashed with a sodium hydroxide solution, thereafter dehydrated by acentrifuge, isolated, and dried at 105° C., whereby a nickel cobaltaluminum composite hydroxide C2 was obtained.

The nickel cobalt aluminum composite hydroxide C2 obtained as describedabove was calcined in an air atmosphere at 600° C. for 8 hours to obtaina nickel cobalt aluminum composite oxide C2.

The obtained nickel cobalt aluminum composite oxide C2 and lithiumhydroxide powder were weighed to achieve Li/(Ni+Co+Al)=1.15 in terms ofmolar ratio and mixed. Thereafter, the mixture was calcined in an oxygenatmosphere at 720° C. for 10 hours to obtain a calcined product C2.

Next, the amount of lithium carbonate remaining in the calcined powderC2 was measured by neutralization titration. Then, a slurry-like liquidwas prepared by adding 1000 g of the calcined product 10 to 2333 g ofpure water at 25° C., the slurry-like liquid was stirred for 10 minuteswhile being maintained at 25° C., and the obtained slurry-like liquidwas subjected to centrifugal filtration to obtain a wet cake.Thereafter, the wet cake was dried at 150° C. for 12 hours to obtain atarget lithium-containing transition metal composite oxide C2.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide C2

Compositional analysis of the obtained positive electrode activematerial C2 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.01,y=0.15, z=0.00, and w=0.03 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material C2 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material C2 for alithium secondary battery are described in Table 1.

In addition, the temperature (° C.) of the washing solution used forwashing, the temperature (° C.) of the slurry, the amount of residuallithium carbonate (g) contained in 1000 g of the calcined product 10,and the saturated dissolution amount (g) when lithium carbonate wasdissolved in 100 g of the washing solution are described in Table 2.

Comparative Example 3 1. Manufacturing of Lithium-Containing TransitionMetal Composite Oxide C3

The amount of lithium carbonate remaining in the calcined product 7obtained in Example 7 was measured by neutralization titration. Then, aslurry-like liquid was prepared by adding 100 g of the calcined product7 to 284.6 g of pure water at 45° C., the slurry-like liquid was stirredfor 20 minutes while being maintained at 45° C., and the obtainedslurry-like liquid was subjected to centrifugal filtration to obtain awet cake. Thereafter, the wet cake was dried at 150° C. for 8 hours toobtain a target lithium-containing transition metal composite oxide C3.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide C3

Compositional analysis of the obtained positive electrode activematerial C3 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.01,y=0.09, z=0.00, and w=0.03 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material C3 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material C3 for alithium secondary battery are described in Table 1.

In addition, the temperature (° C.) of the washing solution used forwashing, the temperature (° C.) of the slurry, the amount of residuallithium carbonate (g) contained in 1000 g of the calcined product 7, andthe saturated dissolution amount (g) when lithium carbonate wasdissolved in 100 g of the washing solution are described in Table 2.

Comparative Example 4 1. Manufacturing of Lithium-Containing TransitionMetal Composite Oxide C4

The amount of lithium carbonate remaining in the calcined product 7obtained in Example 7 was measured by neutralization titration. Then, aslurry-like liquid was prepared by adding 100 g of the calcined product7 to 284.6 g of pure water at 15° C., the slurry-like liquid was stirredfor 20 minutes while being maintained at 15° C., and the obtainedslurry-like liquid was subjected to centrifugal filtration to obtain awet cake. Thereafter, the wet cake was dried at 150° C. for 8 hours toobtain a target lithium-containing transition metal composite oxide C4.

2. Evaluation of Lithium-Containing Transition Metal Composite Oxide C4

Compositional analysis of the obtained positive electrode activematerial C4 for a lithium secondary battery was performed, and when thecomposition was made to correspond to Composition Formula (I), x=0.01,y=0.09, z=0.00, and w=0.03 were obtained.

The γ1/γ2, R, BET specific surface area (m²/g), D₅₀ (μm), D_(max) (μm),D_(min) (μm), and crystallite size L₀₀₃ (Å) of the lithium-containingtransition metal composite oxide contained in the positive electrodeactive material C4 for a lithium secondary battery, and the dischargerate characteristics (described as battery characteristics) of a lithiumsecondary battery using the positive electrode active material C4 for alithium secondary battery are described in Table 1.

In addition, the temperature (° C.) of the washing solution used forwashing, the temperature (° C.) of the slurry, the amount of residuallithium carbonate (g) contained in 1000 g of the calcined product 7, andthe saturated dissolution amount (g) when lithium carbonate wasdissolved in 100 g of the washing solution are described in Table 2.

TABLE 1 Particle Battery Composition xps L₀₀₃ diameter characteristics4.45 V x y z w γ1 γ2 γ1/γ2 R BET (Å) D₅₀ D_(max) D_(min) DCG. 1C DCG. 5C5C/1C Example 1 0.01 0.09 0.02 0.02 0.018 0.037 0.483 0.610 0.25 107411.5 33.9 3.5 187.4 96.3 51.4% Example 2 0.01 0.09 0.02 0.01 0.024 0.0530.452 0.583 0.30 1088 12.9 44.9 3.5 186.2 69.0 37.0% Example 3 0.02 0.090.02 0.02 0.047 0.057 0.830 0.688 0.22 1032 11.2 32.9 3.5 189.6 82.043.3% Example 4 0.00 0.09 0.02 0.02 0.018 0.028 0.630 0.513 0.25 81911.7 36.5 3.5 187.3 63.4 33.9% Example 5 0.01 0.09 0.02 0.02 0.011 0.0270.399 0.505 0.26 787 12.0 37.6 3.5 191.7 57.1 29.8% Example 6 0.00 0.090.02 0.02 0.022 0.027 0.810 0.503 0.23 789 12.0 37.5 3.5 183.2 51.828.3% Example 7 0.01 0.09 0.00 0.03 0.018 0.020 0.900 0.529 1.34 101913.0 53.3 1.2 185.5 71.1 38.3% Example 8 0.04 0.21 0.24 0.00 0.020 0.0260.774 0.503 1.98 875 3.4 11.6 1.0 196.1 183.8 93.7% Example 9 0.02 0.090.00 0.03 0.018 0.019 0.975 0.555 1.43 1059 12.8 53.3 1.2 188.8 66.034.9% Comparative 0.00 0.09 0.02 0.01 0.005 0.026 0.181 0.569 0.35 85111.1 35.4 3.5 205.6 46.8 22.7% Example 1 Comparative 0.00 0.15 0.00 0.030.016 0.011 1.425 0.334 2.50 1074 11.0 33.3 3.8 184.2 39.0 21.2% Example2 Comparative 0.01 0.09 0.00 0.03 0.017 0.013 1.258 0.356 1.44 1006 12.953.3 1.2 182.8 39.2 21.4% Example 3 Comparative 0.01 0.09 0.00 0.030.021 0.015 1.399 0.583 1.41 1032 12.9 47.5 1.2 187.7 49.0 26.1% Example4

TABLE 2 Amount of Tem- lithium perature carbonate contained Saturated ofTem- in 1000 g of solubility of washing perature calcined productlithium carbonate solution of slurry [g/1000 g- [g/100 g- [° C.] [° C.]calcined product] pure water] Example 1 25 25 9.7 1.30 Example 2 25 259.7 1.30 Example 3 25 25 11.3 1.30 Example 4 25 25 10.9 1.30 Example 525 25 10.9 1.30 Example 6 25 25 14.3 1.30 Example 7 5 5 19.1 1.48Example 8 — — — — Example 9 8 8 19.1 1.45 Comparative — — — — Example 1Comparative 25 25 13.1 1.30 Example 2 Comparative 45 45 19.1 1.13Example 3 Comparative 15 15 19.1 1.39 Example 4

As shown in the above results, Examples 1 to 9 to which the presentinvention was applied and which satisfied requirements (1) and (2) hadexcellent discharge rate characteristics. In addition, Examples 1 to 7and Example 9 in which the washing step to which the present inventionwas applied was performed had superior discharge rate characteristics toComparative Example 3 in which the washing step to which the presentinvention was not applied was performed.

In Examples 1 to 6 in which the re-calcining step was performed afterthe washing step, lithium-containing transition metal composite oxidessatisfying requirements (1) and (2) even when the temperature of thewashing solution and the temperature of the slurry were 25° C. wereobtained.

In Example 7, although the re-calcining step after the washing step wasnot performed, since the temperature of the washing solution in thewashing step and the temperature of the slurry were 5° C., alithium-containing transition metal composite oxide satisfyingrequirements (1) and (2) was obtained. In Comparative Examples 2 and 4,the re-calcining step after the washing step was not performed, and thetemperature of the washing solution and the temperature of the slurrywere 25° C. and 15° C., respectively, so that lithium-containingtransition metal composite oxides satisfying requirements (1) and (2)were not obtained.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide alithium-containing transition metal composite oxide for a lithiumsecondary battery having good output characteristics.

REFERENCE SIGNS LIST

-   -   1 Separator    -   2 Positive electrode    -   3 Negative electrode    -   4 Electrode group    -   5 Battery can    -   6 Electrolytic solution    -   7 Top insulator    -   8 Sealing body    -   10 Lithium secondary battery    -   21 Positive electrode lead    -   31 Negative electrode lead    -   X X-ray    -   32 Photoelectron    -   33, 34 Secondary particle

1. A lithium-containing transition metal composite oxide, comprising:secondary particles that are aggregates of primary particles into orfrom which lithium ions are dopable or dedopable, wherein thelithium-containing transition metal composite oxide satisfies thefollowing conditions, (1) the lithium-containing transition metalcomposite oxide is represented by Formula (I),Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I) (in Formula(I), 0≤x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 are satisfied, andM represents one or more metals selected from the group consisting ofMg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y,Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn) (2) when an area valueof a peak appearing at 53.8 eV in a lithium 1s spectrum is referred toas a and an area value of a peak appearing at 529.0 eV in an oxygen 1sspectrum is referred to as β when X-ray photoelectron spectroscopy isperformed, and a ratio between α and β is referred to as γ (α/β=γ), γ iscalculated for each of a surface of the secondary particle and an insideof the secondary particle, and when a γ value of the surface of thesecondary particle is referred to as γ1 and a γ value of the inside ofthe secondary particle is referred to as γ2, γ1 and γ2 satisfy acondition of Formula (II)0.3≤γ1/γ2≤1.0  (II).
 2. The lithium-containing transition metalcomposite oxide according to claim 1, wherein an element ratio R (Li(Atom %)/O (Atom %)) calculated from the peak appearing at 53.8 eV inthe lithium 1s spectrum and the peak appearing at 529.0 eV in the oxygen1s spectrum when the X-ray photoelectron spectroscopy is performed is0.4≤R≤0.8 in the inside of the secondary particle.
 3. Thelithium-containing transition metal composite oxide according to claim1, wherein a BET specific surface area (m²/g) is 0.1 or more and 3.0 orless.
 4. The lithium-containing transition metal composite oxideaccording to claim 1, wherein a crystallite size L₀₀₃ at a peak within arange of 2θ=18.7±1° in a powder X-ray diffraction measurement using CuKαradiation is 400 Å or more and 1300 Å or less.
 5. The lithium-containingtransition metal composite oxide according to claim 1, wherein a 50%cumulative volume particle size D₅₀ (μm) is 3 or more and 20 or less,and a difference between a maximum particle size D_(max) and a minimumparticle size D_(min) (μm) is D₅₀×2/3 or more.
 6. The lithium-containingtransition metal composite oxide according to claim 1, wherein, inFormula (I), 0<x≤0.2 is satisfied.
 7. A positive electrode activematerial for a lithium secondary battery, comprising: thelithium-containing transition metal composite oxide according toclaim
 1. 8. A positive electrode for a lithium secondary battery,comprising: the positive electrode active material for a lithiumsecondary battery according to claim
 7. 9. A lithium secondary battery,comprising: the positive electrode for a lithium secondary batteryaccording to claim
 8. 10. A method for manufacturing alithium-containing transition metal composite oxide including secondaryparticles that are aggregates of primary particles into or from whichlithium ions are dopable or dedopable and represented by General Formula(I), the method comprising: a mixing step of mixing a lithium compoundand a metal composite compound containing at least nickel to obtain amixture; a baking step of baking the mixture to obtain a baked product;and a washing step of washing the baked product, wherein, in the mixingstep, mixing is performed so that a molar ratio (Li/Me, a molar ratio oflithium to a total amount of metal elements excluding lithium) betweenlithium contained in the lithium compound and metal elements in themetal composite compound containing at least nickel exceeds 1, and inthe washing step, a temperature of a washing solution used for washingis set to −20° C. or higher and 40° C. or lower, and washing isperformed in an amount of the washing solution used for washing suchthat a concentration of lithium carbonate in the washing solution in acase where it is assumed that a total amount of residual lithiumcarbonate contained in the baked product before washing is dissolved inthe washing solution is 1/10 or more and 3 or less times a solubility oflithium carbonate in the washing solution at the temperature of thewashing solution during the washing stepLi[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I) (in Formula(I), 0≤x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 are satisfied, andM represents one or more metals selected from the group consisting ofMg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y,Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn).
 11. A method formanufacturing a lithium-containing transition metal composite oxideincluding secondary particles that are aggregates of primary particlesinto or from which lithium ions are dopable or dedopable and representedby General Formula (I), the method comprising: a mixing step of mixing alithium compound and a metal composite compound containing at leastnickel to obtain a mixture; a baking step of baking the mixture toobtain a baked product; and a washing step of washing the baked product,wherein, in the mixing step, mixing is performed so that a molar ratio(Li/Me, a molar ratio of lithium to a total amount of metal elementsexcluding lithium) between lithium contained in the lithium compound andmetal elements in the metal composite compound containing at leastnickel exceeds 1, and in the washing step, a temperature of a slurrycontaining the baked product and a washing solution used for washing ismaintained at −20° C. or higher and lower than 10° C., and washing isperformed in an amount of the washing solution used for washing suchthat a concentration of lithium carbonate in the washing solution in acase where it is assumed that a total amount of residual lithiumcarbonate contained in the baked product before washing is dissolved inthe washing solution is 1/10 or more and 3 or less times a solubility oflithium carbonate in the washing solution at the temperature of thewashing solution during the washing stepLi[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I) (in Formula(I), 0≤x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 are satisfied, andM represents one or more metals selected from the group consisting ofMg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y,Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn).
 12. A method formanufacturing a lithium-containing transition metal composite oxideincluding secondary particles that are aggregates of primary particlesinto or from which lithium ions are dopable or dedopable and representedby General Formula (I), the method comprising: a mixing step of mixing alithium compound and a metal composite compound containing at leastnickel to obtain a mixture; a baking step of baking the mixture toobtain a baked product; and a washing step of washing the baked product,wherein, in the mixing step, mixing is performed so that a molar ratio(Li/Me, a molar ratio of lithium to a total amount of metal elementsexcluding lithium) between lithium contained in the lithium compound andmetal elements in the metal composite compound containing at leastnickel exceeds 1, and in the washing step, a temperature of a washingsolution used for washing is set to −20° C. or higher and 40° C. orlower, washing is performed in an amount of the washing solution usedfor washing such that a concentration of lithium carbonate in thewashing solution in a case where it is assumed that a total amount ofresidual lithium carbonate contained in the baked product before washingis dissolved in the washing solution is 1/10 or more and 3 or less timesa solubility of lithium carbonate in the washing solution at thetemperature of the washing solution, and a temperature of a slurrycontaining the baked product and the washing solution used for washingis maintained at −20° C. or higher and lower than 10° C.Li[Li_(x)(Ni_((1-y-z-w))Co_(y)Mn_(z)M_(w))_(1-x)]O₂  (I) (in Formula(I), 0≤x≤0.2, 0<y≤0.5, 0≤z≤0.8, 0≤w≤0.1, and y+z+w<1 are satisfied, andM represents one or more metals selected from the group consisting ofMg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y,Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn).